JP2024046429A - Electrostatic image developer, process cartridge, image forming apparatus and image forming method - Google Patents

Abstract

[Problem] To provide an electrostatic image developer containing toner particles to which silica particles are externally added and a carrier, which suppresses charge leakage and the occurrence of white spots under high temperature and high humidity conditions even when printing is performed to achieve an extremely high image density. [Solution] An electrostatic image developer containing toner particles, silica particles externally added to the toner particles, which contain a nitrogen-containing compound containing molybdenum, and in which the ratio (Mo/Si) of the net strength of the molybdenum element to the net strength of the silicon element in the silica particles measured by fluorescent X-ray analysis is 0.035 to 0.45, and a carrier having a relative dielectric loss factor of 0.5 to 2.0. [Selected Figure] None

Description

The present invention relates to an electrostatic image developer, a process cartridge, an image forming apparatus, and an image forming method.

Patent Document 1 describes a carrier comprising magnetic core particles and a carrier coating material that coats the surfaces of the magnetic core particles, in which the loss tangent tan δ, which is expressed by the dielectric loss factor ε"/dielectric constant ε' of the carrier, is expressed by the following relational expression:
a/b<6.5, and
0.05<c<20
(Here, a is the DELoss value when the measurement temperature is 30° C. and the frequency DEFreq [Hz] is 1×10 ² , b is the DELoss value when the measurement temperature is 30° C. and the frequency DEFreq [Hz] is 1×10 ⁶ , and c is the DELoss value when the measurement temperature is 150° C. and the frequency DEFreq [Hz] is 1×10 ² .)
A carrier is disclosed which satisfies the following:
Patent Document 2 describes a two-component developer that includes at least first toner particles containing at least a binder resin and a colorant, a first toner containing a first external additive, and a first magnetic carrier, and is used in a developing method in which development is performed while a replenisher containing a second toner and a second magnetic carrier is replenished, the first toner contains at least 0.5 parts by mass or more of first silica particles having a number average particle size of 50 nm or more relative to 100 parts by mass of the first toner particles, and in the loss tangent tan δ of the two-component developer, which is expressed by the dielectric loss factor ε"/dielectric constant ε', the loss tangent tan δ1 at a frequency of 2000 Hz and the loss tangent tan δ2 at a frequency of 2×10 ⁵ Hz satisfy the following formula: 0.06≦tan δ1(2000 Hz)≦0.13
0.04≦tan δ2(2×10 ⁵ Hz)≦0.10
A two-component developer is disclosed which satisfies the above requirements.

JP 2005-257993 A JP 2005-316057 A

In external environments, particularly in high temperature and humidity conditions, charge leakage may occur between the charged toner and the carrier, making it impossible to maintain a high charge. By reducing the dielectric loss factor of the carrier, it becomes possible to achieve high charge and maintain the charge. Here, in printing that requires extremely high image density, it is necessary to increase the electric field during development. However, when the electric field is increased, localized discharge caused by the carrier is likely to occur between the magnetic brush and the image carrier, and the toner may not adhere to the discharged portion, resulting in white spots appearing on the printed matter.
The present invention aims to provide an electrostatic image developer that contains toner particles to which silica particles have been externally added and a carrier, and that suppresses charge leakage and the occurrence of white spots under high temperature and high humidity conditions, even when printing is performed to obtain an extremely high image density.

The invention according to claim 1 provides a toner particle and a silica particle externally added to the toner particle, which contains a nitrogen element-containing compound containing a molybdenum element, and has a net intensity of the molybdenum element measured by fluorescent X-ray analysis. and a ratio (Mo/Si) of the net strength of the silicon element in the silica particles is 0.035 or more and 0.45 or less, and a carrier whose dielectric loss factor is 0.5 or more and 2.0 or less. An electrostatic image developer comprising:
The invention according to claim 2 is the electrostatic image developer according to claim 1, wherein the carrier is made of ferrite, and the ferrite contains at least one of titanium and zirconium.
A third aspect of the invention is the electrostatic image developer according to the second aspect, wherein the carrier has a relative dielectric loss factor of 0.7 or more and 1.7 or less.
The invention according to claim 4 is the electrostatic image developer according to claim 2, wherein the ferrite further contains manganese and magnesium.
The invention according to claim 5 is the electrostatic image developer according to claim 1, wherein the weight ratio of the silica particles to the carrier (silica/carrier) is 0.03 or more and 0.15 or less.
The invention according to claim 6 is the electrostatic image developer according to claim 5, wherein the ratio (Mo/Si) between the net strength of the molybdenum element and the net strength of the silicon element is 0.10 or more and 0.30 or less. It is.
A seventh aspect of the invention is the electrostatic image developer according to the sixth aspect, wherein the nitrogen element-containing compound containing a molybdenum element is a quaternary ammonium salt containing a molybdenum element.
An eighth aspect of the invention is the electrostatic image developer according to the first aspect, wherein the silica particles have a number average particle diameter of 10 nm or more and 100 nm or less.
The invention according to claim 9 provides that the silica particles are composed of a silica mother particle and a reaction product of a trifunctional silane coupling agent that coats at least a part of the surface of the silica mother particle, and that the trifunctional silane 9. The electrostatic image developer according to claim 8, further comprising a structure in which the nitrogen element-containing compound containing the molybdenum element is adsorbed to at least part of the pores of the reaction product of the coupling agent.
The invention according to claim 10 contains the electrostatic image developer according to any one of claims 1 to 9, and forms an electrostatic image formed on the surface of an image carrier by the electrostatic image developer. This is a process cartridge that is equipped with a developing means for developing a toner image and that can be attached to and removed from an image forming apparatus.
The invention according to claim 11 provides the following: an image carrier; a charging means for charging the surface of the image carrier; and an electrostatic image forming means for forming an electrostatic charge image on the charged surface of the image carrier; 9. A developing unit containing the electrostatic image developer according to any one of items 9 to 9, and developing an electrostatic image formed on the surface of the image carrier as a toner image using the electrostatic image developer; The image forming apparatus includes a transfer device that transfers the toner image formed on the surface of the image carrier onto the surface of the recording medium, and a fixing device that fixes the toner image transferred to the surface of the recording medium.
The invention according to claim 12 includes a charging step of charging the surface of an image carrier, an electrostatic charge image forming step of forming an electrostatic charge image on the charged surface of the image carrier, and any one of claims 1 to 9. A developing step of developing the electrostatic charge image formed on the surface of the image carrier as a toner image using the electrostatic charge image developer described in 1. This image forming method includes a transfer step of transferring the toner image onto the surface of the recording medium, and a fixing step of fixing the toner image transferred to the surface of the recording medium.

According to the invention of claim 1, it is possible to provide an electrostatic image developer that contains toner particles to which silica particles have been externally added and a carrier, and that suppresses charge leakage under high temperature and high humidity conditions and suppresses the occurrence of white spots, even when printing is performed with an extremely high image density.
According to the invention of claim 2, the carrier is made of ferrite, and compared to a case in which the ferrite does not contain titanium or zirconium, the dielectric loss factor of the carrier is adjusted, and an electrostatic image developer having appropriate charging properties can be provided.
According to the invention of claim 3, it is possible to provide an electrostatic image developer in which the carrier has favorable charging properties and is capable of suppressing the occurrence of charge leakage, compared with the case in which the dielectric loss factor of the carrier is less than 0.7 or exceeds 1.7.
According to the invention of claim 4, the dielectric loss factor of the carrier is adjusted, and an electrostatic image developer having appropriate charging properties can be provided, compared to a case in which the ferrite in the carrier contains neither manganese nor magnesium.
According to the invention of claim 5, an electrostatic image developer can be provided in which the silica particles have a preferred charge amount and charge leakage through the carrier is suppressed, compared to when the weight ratio of the silica particles to the carrier (silica/carrier) is less than 0.03 or exceeds 0.15.
According to the invention of claim 6, it is possible to provide an electrostatic image developer in which the charging range of silica particles is narrowed, charge leakage is suppressed, and the occurrence of white spots in images is suppressed, as compared with the case where the ratio (Mo/Si) of the net strength of the molybdenum element to the net strength of the silicon element is less than 0.10 or exceeds 0.30.
According to the seventh aspect of the present invention, an electrostatic image developer can be provided in which the charge distribution of silica particles is narrower than when the nitrogen-containing compound containing molybdenum is not a quaternary ammonium salt containing molybdenum.
According to the invention of claim 8, the contact between the carrier and the silica particles is more suitable than when the number average particle diameter of the silica particles is less than 10 nm or exceeds 100 nm, and an electrostatic image developer in which charge leakage is suppressed can be provided.
According to the invention of claim 9, an electrostatic image developer can be provided that can narrow the charge distribution in the silica particles compared to a structure in which the silica particles are not a structure in which at least a portion of the surface of the silica base particle is coated, the silica particles are composed of a reaction product of a trifunctional silane coupling agent, and the nitrogen-element-containing compound is adsorbed into at least a portion of the pores of the reaction product of the trifunctional silane coupling agent.
According to the invention of claim 10, 11 or 12, it is possible to provide a process cartridge, an image forming apparatus or an image forming method capable of applying an electrostatic image developer containing toner particles to which silica particles have been externally added and a carrier, in which charge leakage is suppressed under high temperature and high humidity conditions and the occurrence of white spots is suppressed even when printing is performed with an extremely high image density.

1 is a schematic configuration diagram showing an example of an image forming apparatus according to an embodiment. FIG. 2 is a schematic configuration diagram showing an example of a process cartridge that is attached to and detached from the image forming apparatus according to the present embodiment.

Hereinafter, embodiments of the present invention will be described. The description and examples are merely illustrative of the embodiments, and are not intended to limit the scope of the present invention.
In this disclosure, the descriptions "from XX to XX" or "XX to XX" that express a numerical range mean a numerical range including the stated upper and lower limits, unless otherwise specified. In addition, when referring to the amount of each component in a composition in this disclosure, if the composition contains multiple substances corresponding to each component, the description means the total amount of the multiple substances present in the composition, unless otherwise specified.
In this disclosure, the "electrostatic image developer" may be simply referred to as the "developer", the "electrostatic image developing carrier" may be simply referred to as the "carrier", and the "electrostatic image developing toner" may be simply referred to as the "toner".

In this specification, the characteristics of the silica particles are measured after separation from the toner. There is no limitation on the method for separating the silica particles from the toner, but for example, the silica particles are separated from the toner by the following separation process, and the measurement is performed on the obtained silica particles.
-Separation processing-
2 g of toner is dispersed in 50 g of a 0.2 mass % aqueous solution of Triton X-100 (manufactured by Sigma-Aldrich Corporation), and the dispersion is subjected to ultrasonic waves at 20° C. and 85 WATT for 30 minutes or more using an ultrasonic homogenizer US-300T (manufactured by Nippon Seiki Seisakusho Co., Ltd.). The dispersion is then centrifuged at high speed, and the supernatant is vacuum dried at 80° C. to obtain silica particles.

<Electrostatic image developer>
The electrostatic image developer according to this embodiment is
toner particles;
The silica particles externally added to the toner particles contain a nitrogen element-containing compound containing a molybdenum element, and the net intensity of the molybdenum element and the net intensity of the silicon element in the silica particles are measured by X-ray fluorescence analysis. Silica particles (hereinafter also abbreviated as "specific silica particles") whose ratio (Mo/Si) is 0.035 or more and 0.45 or less,
a carrier having a relative dielectric loss factor of 0.5 or more and 2.0 or less;
including.

In the developer according to this embodiment, by externally adding the specific silica particles to the specific carrier and toner particles, it is possible to suppress the occurrence of white spots that are likely to occur particularly under high temperature and high humidity conditions. . The mechanism is presumed to be as follows.
Particularly when the external environment is high temperature and humidity, charge leakage occurs between the charged toner and the carrier, and a high charge may not be maintained. By reducing the relative dielectric loss factor like the carrier of this embodiment, high charging and charge retention are possible. Here, in printing where the image density is extremely high, it is necessary to increase the electric field during development. However, when the electric field is increased, discharge caused by carriers tends to occur locally between the magnetic brush and the image carrier, and toner may not be deposited on this discharged portion, resulting in white spots appearing on printed matter.
On the other hand, the specific silica particles contain a nitrogen element-containing compound containing molybdenum element. Due to the positive charge derived from the nitrogen element and the high dielectric property mainly composed of molybdenum, excessively high charging can be suppressed and an appropriate charging can be imparted, so that the charging of the developer is stabilized. As a result, it is considered that by combining the carrier of this embodiment, which has a lower relative dielectric loss factor than usual, and the specific silica particles, it becomes possible for the specific silica particles to suppress charge leakage caused by the carrier.
Note that molybdenum has an ionic radius suitable for this effect, and other metals do not have a sufficient effect and no charge leakage suppressing effect has been found.

The toner according to this embodiment will be described in detail below.
The toner according to this embodiment includes toner particles and an external additive.

(Toner Particles)
The toner particles contain a binder resin, and may contain a colorant, a release agent, and other additives, as necessary.

- Binder resin -
Examples of the binder resin include vinyl resins made of homopolymers of monomers such as styrenes (e.g., styrene, parachlorostyrene, α-methylstyrene, etc.), (meth)acrylic acid esters (e.g., methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, etc.), ethylenically unsaturated nitriles (e.g., acrylonitrile, methacrylonitrile, etc.), vinyl ethers (e.g., vinyl methyl ether, vinyl isobutyl ether, etc.), vinyl ketones (e.g., vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl ketone, etc.), and olefins (e.g., ethylene, propylene, butadiene, etc.), or copolymers of two or more of these monomers.
Examples of the binder resin include non-vinyl resins such as epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, and modified rosin, mixtures of these with the vinyl resins, and graft polymers obtained by polymerizing vinyl monomers in the presence of these.
These binder resins may be used alone or in combination of two or more kinds.

The binder resin is preferably a polyester resin.
Examples of the polyester resin include known polyester resins.
The polyester resin may be, for example, a condensation polymer of a polyvalent carboxylic acid and a polyhydric alcohol. The polyester resin may be a commercially available product or a synthesized product.

Examples of polyvalent carboxylic acids include aliphatic dicarboxylic acids (e.g., oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenylsuccinic acid, adipic acid, sebacic acid, etc.), alicyclic dicarboxylic acids (e.g., cyclohexanedicarboxylic acid, etc.), aromatic dicarboxylic acids (e.g., terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, etc.), anhydrides thereof, and lower alkyl esters thereof (e.g., having 1 to 5 carbon atoms). Among these, aromatic dicarboxylic acids are preferable as the polyvalent carboxylic acid.
The polyvalent carboxylic acid may be a trivalent or higher carboxylic acid having a crosslinked or branched structure in combination with a dicarboxylic acid. Examples of the trivalent or higher carboxylic acid include trimellitic acid, pyromellitic acid, anhydrides thereof, and lower (e.g., carbon number 1 to 5) alkyl esters thereof.
The polyvalent carboxylic acids may be used alone or in combination of two or more kinds.

Examples of polyhydric alcohols include aliphatic diols (e.g., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, etc.), alicyclic diols (e.g., cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, etc.), and aromatic diols (e.g., ethylene oxide adducts of bisphenol A, propylene oxide adducts of bisphenol A, etc.). Among these, examples of polyhydric alcohols include aromatic diols and alicyclic diols, and more preferably aromatic diols.
As the polyhydric alcohol, a polyhydric alcohol having a crosslinked or branched structure of three or more may be used in combination with the diol. Examples of the polyhydric alcohol having a trihydric or higher valence include glycerin, trimethylolpropane, and pentaerythritol.
The polyhydric alcohols may be used alone or in combination of two or more kinds.

The glass transition temperature (Tg) of the polyester resin is preferably 50° C. or higher and 80° C. or lower, and more preferably 50° C. or higher and 65° C. or lower.
The glass transition temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC), and more specifically, it is determined from the "extrapolated glass transition onset temperature" described in the method for determining glass transition temperature in JIS K 7121-1987 "Method for measuring transition temperature of plastics."

The weight average molecular weight (Mw) of the polyester resin is preferably 5,000 or more and 1,000,000 or less, more preferably 7,000 or more and 500,000 or less. The number average molecular weight (Mn) of the polyester resin is preferably 2,000 or more and 100,000 or less. The molecular weight distribution Mw/Mn of the polyester resin is preferably 1.5 or more and 100 or less, more preferably 2 or more and 60 or less.
The weight average molecular weight and number average molecular weight of the polyester resin are measured by gel permeation chromatography (GPC). Molecular weight measurement by GPC is performed using a Tosoh GPC/HLC-8120GPC as a measurement device, a Tosoh column/TSKgel SuperHM-M (15 cm), and a THF solvent. The weight average molecular weight and number average molecular weight are calculated from the measurement results using a molecular weight calibration curve prepared using a monodisperse polystyrene standard sample.

Polyester resins are obtained by well-known manufacturing methods. Specifically, it can be obtained, for example, by a method in which the polymerization temperature is set at 180° C. or more and 230° C. or less, the pressure inside the reaction system is reduced as necessary, and the reaction is carried out while removing water and alcohol generated during condensation.
In addition, when the raw material monomers are not dissolved or compatible at the reaction temperature, a high boiling point solvent may be added as a solubilizing agent to dissolve them. In this case, the polycondensation reaction is carried out while distilling off the solubilizing agent. If there are monomers with poor compatibility in the copolymerization reaction, the monomers with poor compatibility and the acid or alcohol to be polycondensed are condensed in advance, and then the monomers are copolymerized with the main component. Condensation is recommended.
The content of the binder resin is, for example, preferably 40% by mass or more and 95% by mass or less, more preferably 50% by mass or more and 90% by mass or less, and 60% by mass or more and 85% by mass or less, based on the entire toner particles. More preferred.

- Coloring agent -
Examples of colorants include various pigments such as carbon black, chrome yellow, Hansa yellow, benzidine yellow, threne yellow, quinoline yellow, pigment yellow, permanent orange GTR, pyrazolone orange, Balkan orange, watch young red, permanent red, brilliant carmine 3B, brilliant carmine 6B, DuPont oil red, pyrazolone red, lithol red, rhodamine B lake, lake red C, pigment red, rose bengal, aniline blue, ultramarine blue, chalco oil blue, methylene blue chloride, phthalocyanine blue, pigment blue, phthalocyanine green, and malachite green oxalate, and various dyes such as acridine-based, xanthene-based, azo-based, benzoquinone-based, azine-based, anthraquinone-based, c-based, dioxazine-based, thiazine-based, azomethine-based, indigo-based, phthalocyanine-based, aniline black-based, polymethine-based, triphenylmethane-based, diphenylmethane-based, and thiazole-based dyes.
The colorant may be used alone or in combination of two or more kinds.
The colorant may be surface-treated as necessary, or may be used in combination with a dispersant. In addition, a plurality of types of colorants may be used in combination.
The content of the colorant is, for example, preferably from 1% by mass to 30% by mass, and more preferably from 3% by mass to 15% by mass, based on the total mass of the toner particles.

-Release agent-
Examples of mold release agents include hydrocarbon waxes; natural waxes such as carnauba wax, rice wax, and candelilla wax; synthetic or mineral/petroleum waxes such as montan wax; and ester waxes such as fatty acid esters and montanic acid esters. ; etc. The mold release agent is not limited to this.
The melting temperature of the mold release agent is preferably 50°C or more and 110°C or less, more preferably 60°C or more and 100°C or less.
The melting temperature is determined from the DSC curve obtained by differential scanning calorimetry (DSC) using the "melting peak temperature" described in the method for determining the melting temperature of JIS K 7121-1987 "Method for measuring transition temperature of plastics". .
The content of the release agent is preferably 1% by mass or more and 20% by mass or less, more preferably 5% by mass or more and 15% by mass or less, based on the entire toner particles.

-Other additives-
Examples of other additives include well-known additives such as magnetic substances, charge control agents, and inorganic powders. These additives are included in the toner particles as internal additives.

-Characteristics of toner particles-
The toner particles may be toner particles having a single layer structure, or may be toner particles having a so-called core-shell structure composed of a core portion (core particle) and a coating layer (shell layer) that coats the core portion.
Here, the toner particles having a core-shell structure may be composed of, for example, a core containing a binder resin and, if necessary, other additives such as a colorant and a release agent, and a coating layer containing the binder resin.

The volume average particle diameter (D50v) of the toner particles is preferably 2 μm or more and 10 μm or less, more preferably 4 μm or more and 8 μm or less.

The various average particle sizes and particle size distribution indexes of the toner particles are measured using a Coulter Multisizer II (manufactured by Beckman Coulter, Inc.), and the electrolyte is measured using an ISOTON-II (manufactured by Beckman Coulter, Inc.).
For the measurement, 0.5 mg to 50 mg of a measurement sample is added to 2 ml of a 5% aqueous solution of a surfactant (preferably sodium alkylbenzene sulfonate) as a dispersant, and this is then added to 100 ml to 150 ml of an electrolyte.
The electrolyte in which the sample was suspended was subjected to dispersion treatment for 1 minute using an ultrasonic disperser, and the particle size distribution of particles with a particle size range of 2 μm to 60 μm was measured using a Coulter Multisizer II with an aperture diameter of 100 μm. The number of particles sampled was 50,000.
Based on the measured particle size distribution, cumulative distributions of volume and number are drawn for each divided particle size range (channel) from the small diameter side, and the particle size at 16% of the cumulative size is defined as the volume particle size D16v, the number particle size D16p, the particle size at 50% of the cumulative size as the volume average particle size D50v, the cumulative number average particle size D50p, and the particle size at 84% of the cumulative size as the volume particle size D84v and the number particle size D84p.
Using these, the volume particle size distribution index (GSDv) is calculated as (D84v/D16v) ^1/2 , and the number particle size distribution index (GSDp) is calculated as (D84p/D16p) ^1/2 .

The average circularity of the toner particles is preferably 0.950 or more and 0.990 or less, more preferably 0.957 or more and 0.980 or less.
The average circularity of toner particles is measured using FPIA-3000 manufactured by Sysmex. This device uses a flow-type image analysis method to measure particles dispersed in water, etc. The aspirated particle suspension is guided to a flat sheath flow cell, and the sheath liquid creates a flat sample flow. It is formed. By irradiating the sample flow with strobe light, the passing particles are imaged as a still image by a CCD (Charge Coupled Device) camera through an objective lens. The captured particle image is subjected to two-dimensional image processing to calculate circularity from the projected area and perimeter. Regarding circularity, the average circularity is determined by analyzing at least 4,000 images and performing statistical processing.
・Formula: Circularity = Equivalent circle diameter Perimeter length / Perimeter length = [2 × (Aπ) ^1/2 ] / PM
In the above formula, A represents the projected area and PM represents the perimeter.
Note that HPF mode (high resolution mode) is used for the measurement, and the dilution rate is 1.0 times. Furthermore, in data analysis, the circularity analysis range is set to 0.40 or more and 1.00 or less for the purpose of removing measurement noise.

(External additives)
The external additive added to the toner particles contains specific silica particles.
The specific silica particles contain a nitrogen-containing compound containing molybdenum, and the ratio (Mo/Si) of the net intensity of the molybdenum element to the net intensity of the silicon element in the silica particles, as measured by fluorescent X-ray analysis, is 0.035 or more and 0.45 or less.

-Nitrogen-containing compounds including molybdenum-
The specific silica particles contain a nitrogen-containing compound, and the nitrogen-containing compound further contains molybdenum. As described below, the nitrogen-containing compound is preferably adsorbed in at least a part of the pores of the reaction product of the trifunctional silane coupling agent.
From the viewpoint of suppressing image unevenness and toner scattering by narrowing the charge distribution of the silica particles, the nitrogen-containing compound containing molybdenum is preferably at least one selected from the group consisting of quaternary ammonium salts containing molybdenum (particularly, quaternary ammonium salts containing molybdenum) and mixtures of quaternary ammonium salts and metal oxides containing molybdenum.
The nitrogen element compound contains molybdenum element, which enhances the activity of nitrogen element, and even if the nitrogen element-containing compound is present inside the pores of the silica particles instead of on the outermost surface, the positive chargeability of the nitrogen element can be appropriately expressed. Therefore, when charged, the charge distribution is narrow, and the charge distribution is easily maintained. As a result, it is easy to realize the suppression of image unevenness and the suppression of toner scattering. And, by combining with the carrier described later, the charge leakage can be suppressed, and the occurrence of white spots in printing can also be suppressed.
In particular, in the case of a quaternary ammonium salt containing molybdenum, the anion containing molybdenum, which is an anion, is strongly bonded to the quaternary ammonium cation, which is a cation, and therefore the charge distribution can be maintained more effectively, which makes it easier to suppress image unevenness and toner scattering.

^{Examples of quaternary ammonium salts containing molybdenum include [N+(CH)3(C14C29)2]4Mo8O284-} _, ^[ _{N + ( C4H9 )} ² _{( C6H6 ) 2 ] 2Mo2O72-} ^, _[ ^{N +} ( _{CH3 ) 2 ( CH2C6H6} ) _{( CH2 ) 17CH3 ] 2MoO42- ,} ^and [N ₊ ( _CH3 ⁾ _{2 ( CH2C6H6} ) _{( CH2 ) 15CH3} ] _{2MoO42- .}
Examples of metal oxides containing molybdenum include molybdenum oxides (molybdenum trioxide, molybdenum dioxide _{, Mo9O26} ), alkali metal molybdates (lithium molybdate, sodium molybdate, potassium molybdate, etc.), alkaline earth metal molybdates (magnesium molybdate, calcium _molybdate , etc.), and other composite oxides such as _{Bi2O3.2MoO3 and γ - Ce2Mo3O13} .

Here, when a nitrogen-containing compound containing molybdenum is used as the nitrogen-containing compound, from the viewpoints of suppressing image unevenness, suppressing toner scattering, and controlling white spots by narrowing the charge distribution of silica particles under specific conditions, the ratio of net intensity of molybdenum to net intensity of silicon measured by fluorescent X-ray analysis (Mo/Si) is 0.035 or more and 0.45 or less, preferably 0.07 or more and 0.32 or less, more preferably 0.10 or more and 0.30 or less.
From the viewpoint of suppressing image unevenness and toner scattering by narrowing the charge distribution of silica particles under specific conditions, the net strength of molybdenum element is preferably 5 kcps to 75 kcps, 7 kcps to 50 kcps, 8 kcps to 55 kcps, or 10 kcps to 40 kcps.

The net strength of molybdenum element and silicon element is measured as follows.
Approximately 0.5 g of silica particles are compressed using a compression molding machine under pressure of 6 tons for 60 seconds to produce a disk with a diameter of 50 mm and a thickness of 2 mm. Using this disk as a sample, qualitative and quantitative elemental analysis was performed using a scanning X-ray fluorescence analyzer (XRF-1500, manufactured by Shimadzu Corporation) under the following conditions, and the net intensities of molybdenum element and silicon element were determined. (Unit: kilo counts per second, kcps) is calculated.
・Tube voltage: 40kV
・Tube current: 90mA
・Measurement area (analysis diameter): diameter 10mmφ
・Measurement time: 30 minutes ・Anticathode: Rhodium

-Detection and content of nitrogen element-containing compounds-
When the specific silica particles are heated in a temperature range of 300°C or higher and 600°C or lower, nitrogen element-containing compounds are detected. Specifically, for example, it is as follows.
For detection of nitrogen element-containing compounds, for example, a heating furnace type falling pyrolysis gas chromatograph mass spectrometer using He as a carrier gas is used. A nitrogen element-containing compound containing molybdenum element can be detected under a thermal decomposition temperature condition of 300° C. or more and 600° C. or less under an inert gas. Specifically, silica particles of 0.1 mg or more and 10 mg or less are introduced into a pyrolysis gas chromatograph mass spectrometer, and the presence or absence of a nitrogen element-containing compound containing molybdenum element can be confirmed from the MS spectrum of the detected peak. .
From the viewpoint of suppressing image unevenness and toner scattering by narrowing the charge distribution of the silica particles, the content of the nitrogen element-containing compound containing the molybdenum element should be 0.005% by mass or more in terms of nitrogen element based on the silica particles. .5% by mass or less. The content is preferably 0.05% by mass or more and 0.4% by mass or less, more preferably 0.1% by mass or more and 0.3% by mass or less.

Further, the content of the nitrogen element-containing compound containing molybdenum element in terms of nitrogen element is measured as follows.
Using an oxygen/nitrogen analyzer (for example, EMGA-920 manufactured by Horiba, Ltd.), the measurement is performed for an integrated time of 45 seconds, and the amount of nitrogen present is obtained as the ratio of N (N/Si). As sample pretreatment, impurities such as ammonia are removed from the silica particles by drying the sample at 100° C. for 24 hours or more in a vacuum dryer.

- Extraction amount of nitrogen-containing compounds including molybdenum -
It is preferable that the amount X of the nitrogen-containing compound including molybdenum extracted by the ammonia/methanol mixed solution is 0.1% by mass or more relative to 100% by mass of the silica particles, and the amount X of the nitrogen-containing compound extracted by the water and the amount Y of the nitrogen-containing compound extracted by the water (which is also the mass % relative to 100% by mass of the silica particles as with X) satisfy the formula: Y/X<0.3.
That is, the nitrogen-containing compound containing molybdenum is difficult to dissolve in water, that is, it is difficult to adsorb moisture in the air.
In silica particles containing a nitrogen-containing compound that also contains molybdenum, when the compound adsorbs moisture, the charge distribution becomes wider and the nitrogen-containing compound that also contains molybdenum becomes more likely to separate from the silica particles.
However, silica particles containing nitrogen-containing compounds containing molybdenum, which are difficult to adsorb moisture in air, are difficult to widen the charge distribution even when there is a lot of moisture in the air (even under high humidity), and the nitrogen-containing compounds are difficult to separate, so that a narrow charge distribution is easily maintained.As a result, the charge distribution of silica particles is narrowed under specific conditions, which makes it easy to realize the suppression of image unevenness and toner scattering.

The extraction amount X of the nitrogen-containing compound containing molybdenum is preferably 0.25% by mass or more relative to 100% by mass of the silica particles, but the upper limit of the extraction amount X of the nitrogen-containing compound containing molybdenum is, for example, 6.5% by mass or less, because the solution is difficult to penetrate into the pores due to surface tension, and a part of the nitrogen-containing compound containing molybdenum remains undissolved.
The ratio "Y/X" of the amount of extraction X of the nitrogen-containing compound containing molybdenum to the amount of extraction Y of the compound is preferably less than 0.3, more preferably 0.15 or less. However, the lower limit of the ratio "Y/X" is ideally 0, but since the measurement error range of X and Y is about ±1%, it is, for example, 0.01 or more.

Here, the extracted amounts X and Y of the nitrogen-containing compound containing molybdenum are measured as follows.
First, the silica particles to be measured are analyzed at a constant temperature of 400°C using a thermogravimetric/mass spectrometer (e.g., a gas chromatograph mass spectrometer manufactured by Netzsch Japan Co., Ltd.), and the integrated mass fraction of compounds in which a hydrocarbon having at least one carbon atom is covalently bonded to a nitrogen atom relative to the silica particles is measured and designated as W1.

On the other hand, 1 part by mass of silica particles to be measured was added to 30 parts by mass of an ammonia/methanol solution (manufactured by Sigma-Aldrich, mass ratio of ammonia/methanol = 1/5.2) at a liquid temperature of 25°C, and the mixture was heated for 30 minutes. After ultrasonication, the silica powder and the extract are separated. The separated silica particles were dried in a vacuum dryer at 100°C for 24 hours, and a thermogravimetric/mass spectrometer was used to test them at 400°C under constant conditions to obtain silica particles of a compound in which a hydrocarbon having at least 1 carbon atom was covalently bonded to a nitrogen atom. The mass fraction with respect to that is measured and designated as W2.
Then, the extraction amount X of the nitrogen element-containing compound is calculated using the following formula.
・Formula: X=W1-W2

In addition, 1 part by mass of silica particles to be measured is added to 30 parts by mass of water at a liquid temperature of 25° C., and after ultrasonic treatment for 30 minutes, the silica particles and the extract are separated. The separated silica particles are dried in a vacuum dryer at 100° C. for 24 hours, and the mass fraction of compounds in which a hydrocarbon having at least one carbon atom is covalently bonded to a nitrogen atom is measured with a thermogravimetric/mass spectrometer at a constant temperature of 400° C., and this mass fraction is designated as W3.
Then, the amount Y of the extracted nitrogen-containing compound containing molybdenum is calculated by the following formula.
Formula: Y = W1 - W3

-Pore volume-
In the specific silica particles, when the pore volumes A and B are the pore diameters of 1 nm or more and 50 nm or less obtained from the pore distribution curve of the nitrogen gas adsorption method before and after baking at 350°C, respectively, it is preferable that B/A is 1.2 or more and 5 or less, and B is 0.2 ^cm3 /g or more and ³ cm3/g or less.
In the specific silica particles, the ratio B/A of the pore volume B after baking at 350° C. to the pore volume A before baking at 350° C. is preferably 1.2 to 5. If the ratio is too small, the nitrogen-containing compound is easily desorbed and the charge sustaining effect tends not to be obtained, and if the ratio is too large, the nitrogen-containing compound penetrates too far into the silica particles, resulting in insufficient electrostatic repulsion and insufficient adhesion reducing effect. From these viewpoints, the ratio is more preferably 1.5 to 4.5, and even more preferably 2.5 to 3.5.
The pore volume B after firing at 350°C is preferably 0.2 ^cm3 /g or more and 3 ^cm3 /g or less. If it is too small, the nitrogen-containing compound is likely to be easily detached and the electrostatic charge sustaining effect tends not to be obtained, and if it is too large, the nitrogen-containing compound tends to penetrate too far inside the silica particles, resulting in insufficient electrostatic repulsion and insufficient adhesion reduction effect. From these viewpoints, the pore volume B is more preferably ^0.5 cm3/g or more and 2.5 ^cm3 /g or less, and even more preferably 1.0 ^cm3 /g or more and 2.0 ^cm3 /g or less.
From the viewpoint of allowing easy penetration of nitrogen elements and maintaining an appropriate electrostatic repulsion effect, the pore volume A before firing at 350°C is preferably 0.1 ^cm3 /0.9 g or more and ^cm3 /g or less, more preferably 0.3 ^cm3 /g or more and 0.7 ^cm3 /g or less, and even more preferably 0.4 ^cm3 /g or more and 0.6 ^cm3 /g or less.

Specifically, the 350° C. firing is carried out as follows.
In a nitrogen environment, the silica particles to be measured are heated to 350° C. at a heating rate of 10° C./min and held at 350° C. for 3 hours. Thereafter, the particles are cooled to room temperature (25° C.) at a heating rate of 10° C./min.

Pore volume is measured as follows.
First, the silica particles to be measured are cooled to liquid nitrogen temperature (-196°C), nitrogen gas is introduced, and the amount of adsorption is determined by a constant volume method or a gravimetric method. The pressure of the introduced nitrogen gas is gradually increased, and an adsorption isotherm is created by plotting the amount of adsorption of nitrogen gas for each equilibrium pressure. From this adsorption isotherm, a pore size distribution curve is calculated using the BJH method formula, with the vertical axis representing frequency and the horizontal axis representing pore diameter.
From the obtained pore size distribution curve, an integrated pore volume distribution is calculated, where the vertical axis is volume and the horizontal axis is pore diameter. From the obtained integrated pore volume distribution, the pore volumes in the pore diameter range of 1 nm to 50 nm are integrated, and this is defined as the "pore volume with a pore diameter of 1 nm to 50 nm."

-CP/MAS NMR spectrum-
In the specific silica particles, the ratio C/E of an integral value C of a signal observed in a chemical shift range of −50 ppm or more and −75 ppm or less in a Si-CP/MAS NMR spectrum to an integral value D of a signal observed in a chemical shift range of −90 ppm or more and −120 ppm or less is preferably 0.10 or more and 0.75 or less, but from the viewpoint of suppressing image unevenness and suppressing toner scattering by narrowing the charge distribution of the silica particles, it is more preferably 0.12 or more and 0.45 or less, and even more preferably 0.15 or more and 0.40 or less.
From the viewpoint of narrowing the charge distribution of the silica particles and suppressing image unevenness, when the integral value of all signals in the Si-CP/MAS NMR spectrum is taken as 100%, the ratio of the integral value C of signals observed in the chemical shift range of -50 ppm to -75 ppm (signal ratio) is preferably 5% or more, more preferably 7% or more. The upper limit of the ratio of the integral value C of the signals is, for example, 60% or less.

The Si-CP/MAS NMR spectrum is obtained by carrying out measurements using nuclear magnetic resonance spectroscopy under the following conditions.
・Spectrometer: AVENCE300 (manufactured by Brunker)
・Resonance frequency: 59.6MHz
・Measurement nucleus: ²⁹ Si
・Measurement method: CPMAS method (using Bruker standard pulse sequence cp.av)
・Waiting time: 4 seconds ・Contact time: 8 milliseconds ・Number of integration: 2048 times ・Measurement temperature: Room temperature (actual value 25℃)
・Observation center frequency: -3975.72Hz
・MAS rotation speed: 7.0mm-6kHz
・Reference material: hexymethylcyclotrisiloxane

- Composition of silica particles -
The specific silica particles contain a nitrogen element-containing compound containing molybdenum element.
As a specific example, the specific silica particles are coated with a reaction product of a silica base particle and at least a portion of the surface of the silica base particle, and further coated with a reaction product of a trifunctional silane coupling agent. An example of this structure is a structure in which a nitrogen element-containing compound containing molybdenum element is adsorbed. By forming the structure, the pore volume characteristics and the Si-CP/MASNMR spectrum characteristics can be controlled. Furthermore, the degree of hydrophobicity and the amount of OH groups, which will be described later, can also be controlled.
Further, the specific silica particles may have a hydrophobized structure on the surface of the structure.

-Silica base particles-
At least a portion of the surface of the silica mother particles is composed of a reaction product of a trifunctional silane coupling agent, and a nitrogen element-containing compound is formed in at least a portion of the pores of the reaction product of the trifunctional silane coupling agent. These are silica particles on which adsorbed structures are formed.
Examples of the silica base particles include dry silica particles and wet silica particles.
Examples of dry silica particles include combustion method silica (fumed silica) obtained by burning a silane compound and deflagration method silica obtained by explosively burning metal silicon powder.
Wet silica particles include wet silica particles obtained by neutralizing sodium silicate and mineral acids (precipitation method silica synthesized and flocculated under alkaline conditions, gel method silica particles synthesized and flocculated under acidic conditions), and acidic silica particles. Examples include colloidal silica particles (silica sol particles) obtained by alkaline polymerization and sol-gel silica particles obtained by hydrolyzing an organic silane compound (eg, alkoxysilane).
Among these, sol-gel method silica particles are preferable as the silica base particles from the viewpoint of suppressing image unevenness and toner scattering by narrowing the charge distribution of the silica particles.

-Reaction product of trifunctional silane coupling agent-
The adsorption structure composed of the reaction product of a trifunctional silane coupling agent has a low density and a structure that has high affinity for nitrogen element-containing compounds, so nitrogen element-containing compounds are easily adsorbed deep into the pores. The adsorption amount (ie, content) of nitrogen element-containing compounds increases. By adhering the positively chargeable nitrogen element-containing compound to the negatively chargeable silica surface, an effect of canceling out excessive negative charge is generated. In addition, since the nitrogen element-containing compound is not adsorbed on the outermost surface of the silica particles but inside the low-density structure, it prevents the positive chargeability from becoming too strong and the charge distribution spreads, and cancels out only the excessive negative charge. This improves the narrowing of the charge distribution. As a result, it becomes easier to suppress image unevenness and toner scattering by narrowing the charge distribution of silica particles under specific conditions.

Examples of the reaction product of a trifunctional silane coupling agent include a reaction product in which OR ² is substituted with an OH group in the following general formula (TA), a reaction product in which OR ² is substituted with an OH group is polycondensed with each other, and a reaction product in which OR ² is substituted with an OH group is polycondensed with the SiOH group of silica particles. The reaction product of a trifunctional silane coupling agent includes a reaction product in which all or a part of OR ² is substituted, and a reaction product in which all or a part of OR 2 is polycondensed.
The trifunctional silane coupling agent is a non-nitrogen element-containing compound that does not contain N (nitrogen).
Specifically, the trifunctional silane coupling agent may be a trifunctional silane coupling agent represented by the following general formula (TA).
General formula (TA): R ¹ -Si(OR ² ) ₃

In general formula (TA), ^R1 represents a saturated or unsaturated aliphatic hydrocarbon group having from 1 to 20 carbon atoms or an aromatic hydrocarbon group having from 6 to 20 carbon atoms, and ^R2 represents a halogen atom or an alkoxy group. A plurality of ^R2 may be the same group or different groups.
The aliphatic hydrocarbon group represented by ^R1 may be linear, branched, or cyclic, but is preferably linear or branched. The carbon number of the aliphatic hydrocarbon group is preferably 1 to 20, more preferably 1 to 18, even more preferably 1 to 12, and even more preferably 1 to 10. The aliphatic hydrocarbon group may be either saturated or unsaturated, but is preferably a saturated aliphatic hydrocarbon group, and more preferably an alkyl group.

Examples of saturated aliphatic hydrocarbon groups include linear alkyl groups (methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, hexadecyl, and icosyl groups, etc.), branched alkyl groups (isopropyl, isobutyl, isopentyl, neopentyl, 2-ethylhexyl, tertiary butyl, tertiary pentyl, and isopentadecyl groups, etc.), and cyclic alkyl groups (cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, tricyclodecyl, norbornyl, and adamantyl groups, etc.).

Examples of unsaturated aliphatic hydrocarbon groups include alkenyl groups (vinyl groups (ethenyl groups), 1-propenyl groups, 2-propenyl groups, 2-butenyl groups, 1-butenyl groups, 1-hexenyl groups, 2-dodecenyl groups, pentenyl groups, etc.), and alkynyl groups (ethynyl groups, 1-propynyl groups, 2-propynyl groups, 1-butynyl groups, 3-hexynyl groups, 2-dodecenyl groups, etc.).

The aromatic hydrocarbon group represented by ^R1 preferably has 6 to 20 carbon atoms, more preferably 6 to 18 carbon atoms, even more preferably 6 to 12 carbon atoms, and still more preferably 6 to 10 carbon atoms.
Examples of the aromatic hydrocarbon group include a phenylene group, a biphenylene group, a terphenylene group, a naphthalene group, and an anthracene group.

Examples of the halogen atom represented by R ² include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, and the like. The halogen atom is preferably a chlorine atom, a bromine atom, or an iodine atom.
Examples of the alkoxy group represented by R ² include alkoxy groups having 1 or more and 10 or less carbon atoms (preferably 1 or more and 8 or less, more preferably 1 or more and 4 or less). Examples of the alkoxy group include methoxy group, ethoxy group, isopropoxy group, t-butoxy group, n-butoxy group, n-hexyloxy group, 2-ethylhexyloxy group, 3,5,5-trimethylhexyloxy group, etc. It will be done. Alkoxy groups also include substituted alkoxy groups. Examples of substituents that can be substituted on an alkoxy group include a halogen atom, a hydroxyl group, an amino group, an alkoxy group, an amide group, and a carbonyl group.

The trifunctional silane coupling agent represented by the general formula (TA) is a trifunctional silane coupling agent in which R ¹ is a saturated aliphatic hydrocarbon group having 1 to 20 carbon atoms, and R ² is a halogen atom or an alkoxy group. Ring agents are preferred.

As the trifunctional silane coupling agent, for example,
Vinyltrimethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, hexyltrimethoxysilane, n-octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, vinyltriethoxy Silane, methyltriethoxysilane, ethyltriethoxysilane, butyltriethoxysilane, hexyltriethoxysilane, decyltriethoxysilane, dodecyltriethoxysilane, phenyltrimethoxysilane, o-methylphenyltrimethoxysilane, p-methylphenyltriethoxysilane Methoxysilane, phenyltriethoxysilane, benzyltriethoxysilane, decyltrichlorosilane, phenyltrichlorosilane (compounds in which R ¹ is an unsubstituted aliphatic hydrocarbon group or an unsubstituted aromatic hydrocarbon group);
3-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-glycidyloxypropylmethyldimethoxysilane (where R ¹ is a compound that is a substituted aliphatic hydrocarbon group or a substituted aromatic hydrocarbon group);
Examples include.
One type of trifunctional silane coupling agent may be used alone, or two or more types may be used in combination.

Among these, from the viewpoint of suppressing image unevenness and toner scattering by narrowing the charge distribution of the silica particles, alkyltrialkoxysilanes are preferred as the trifunctional silane coupling agents, and alkyltrialkoxysilanes in which, in general formula (TA), R ¹ represents an alkyl group having 1 to 20 carbon atoms (preferably, 1 to 15 carbon atoms) and R ² represents an alkyl group having 1 to 2 carbon atoms are more preferred.

The amount of the structure composed of the reaction product of the trifunctional silane coupling agent attached is preferably 5.5% by mass or more and 30% by mass or less, and more preferably 7% by mass or more and 22% by mass or less, based on the silica particles, from the viewpoint of suppressing image unevenness and toner scattering by narrowing the charge distribution of the silica particles under specific conditions.

The nitrogen element-containing compound containing the molybdenum element is preferably adsorbed to at least a portion of the pores of the reaction product of the trifunctional silane coupling agent.

(Hydrophobized structure)
The hydrophobized structure is a structure reacted with a hydrophobization treatment agent.
As the hydrophobizing agent, for example, an organosilicon compound is applied.
Examples of organosilicon compounds include:
Alkoxysilane compounds or halosilane compounds having a lower alkyl group such as methyltrimethoxysilane, dimethyldimethoxysilane, trimethylchlorosilane, trimethylmethoxysilane;
Alkoxysilane compounds having a vinyl group such as vinyltrimethoxysilane and vinyltriethoxysilane;
2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycid Alkoxysilane compounds having epoxy groups such as oxypropyltriethoxysilane;
Alkoxysilane compounds having a styryl group such as p-styryltrimethoxysilane and p-styryltriethoxysilane;
N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, Alkoxysilane compounds having an aminoalkyl group such as 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine and N-phenyl-3-aminopropyltrimethoxysilane;
Alkoxysilane compounds having an isocyanate alkyl group such as 3-isocyanatepropyltrimethoxysilane and 3-isocyanatepropyltriethoxysilane;
Silazane compounds such as hexamethyldisilazane and tetramethyldisilazane;
Examples include.

(Characteristics of silica particles)
-Hydrophobicity-
The degree of hydrophobicity of the specific silica particles is preferably 10% or more and 60% or less, and 20% or more and 55% or less, from the viewpoint of suppressing image unevenness and toner scattering by narrowing the charge distribution of the silica particles under specific conditions. More preferably, it is 28% or more and 53% or less.
If the degree of hydrophobicity of the silica particles is 10% or less, the coverage of the structure will be low due to the reaction formation of the trifunctional silane coupling agent, and the content of the nitrogen element-containing compound will be reduced, so that the charge distribution will tend to spread. Become.
On the other hand, when the degree of hydrophobicity of the silica particles exceeds 60%, the density of the structure increases due to the reaction formation of the trifunctional silane coupling agent, the number of pores decreases, and the content of the nitrogen element-containing compound decreases. Therefore, the charge distribution tends to spread. As a result, it becomes easier to suppress image unevenness and toner scattering by narrowing the charge distribution of the silica particles.

The degree of hydrophobicity of silica particles is measured as follows.
Add 0.2% by mass of silica particles as a sample to 50ml of ion-exchanged water, add methanol dropwise from a buret while stirring with a magnetic stirrer, and calculate the mass fraction of methanol in the methanol-water mixed solution at the end point when the entire sample has sunk. is determined as the degree of hydrophobicity.

--Number average particle size and number particle size distribution index--
The number average particle diameter of the specific silica particles is preferably 10 nm or more and 100 nm or less, more preferably 10 nm or more and 80 nm or less, and even more preferably 10 nm or more and 70 nm or less.
When the number-average particle diameter of the silica particles is within the above range, the contact with the carrier is favorable, and the charge leakage is appropriately controlled, thereby suppressing the generation of white spots. (When the particle diameter is smaller than 10 nm, the particles are easily buried in the toner surface or other external additives, and the effect is not easily obtained. When the particle diameter is larger than 100 nm, the particles are not easily retained in the toner, and the effect is not easily obtained.)
The number particle size distribution index of the specific silica particles is preferably 1.1 or more and 2.0 or less, and more preferably 1.15 or more and 1.6 or less.
When the number particle size distribution index of the specific silica particles is within the above range, the amount of coarse powder that tends to have a large charge amount and the amount of fine powder that tends to have a small charge amount are small, and the charge distribution is easily narrowed. As a result, the charge distribution of the silica particles is narrowed, which makes it easy to suppress image unevenness and toner scattering.

Here, the number average particle diameter and number particle size distribution index of silica particles are measured as follows.
The silica particles were observed using a scanning electron microscope (SEM) at a magnification of 40,000 times, and the images of the observed silica particles were analyzed using the image processing analysis software WinRoof (manufactured by Mitani Shoji Co., Ltd.) to identify circles of at least 200 particles. Find the equivalent diameter. Then, a cumulative distribution is drawn for the number of individual particles starting from the small diameter side, and the particle size and number average particle diameter that give a cumulative 50% from the small diameter side are determined.

Further, from the small diameter side, the square root of the value obtained by dividing the particle size D84, which is cumulatively 84%, by the particle size D16, which is cumulatively 16%, is defined as a "number particle size distribution index" (GSD). That is, number particle size distribution index (GSD) = (D84/D16) ^0.5 .

-Circularity-
The average circularity of the specific silica particles is preferably 0.60 or more and 0.96 or less, more preferably 0.70 or more and 0.92 or less, and even more preferably 0.75 or more and 0.90 or less.
When the average circularity of the silica particles is within the above range, the specific surface area is large and excessive charging is likely to occur, but even when the average circularity of the specific silica particles is within the above range, the charging distribution can be narrowed. As a result, even if the average circularity of the specific silica particles is within the above range, image unevenness and toner scattering can be easily suppressed by narrowing the charge distribution of the silica particles.

Here, the circularity of the silica particles is measured as follows.
Silica particles are observed at 40,000 times magnification using a scanning electron microscope (SEM), and the images of the observed silica particles are analyzed using image processing analysis software WinRoof (manufactured by Mitani Shoji Co., Ltd.) to determine the circularity of at least 200 particles, and the average circularity is calculated by arithmetic averaging.
The circularity is calculated according to the following formula.
Circularity = equivalent circle diameter / circumference = [2 × (Aπ) ^1/2 ] / PM
In the above formula, A represents the projected area, and PM represents the perimeter.

-Volume resistivity-
The volume resistivity of the specific silica particles (that is, the volume resistivity before firing at 350° C.) is preferably 1.0×10 ⁷ Ωcm or more and 1.0×10 ^11.5 Ωcm or less, and more preferably 1.0×10 ⁸ Ωcm or more and 1.0×10 ¹¹ Ωcm or less.
When the volume resistivity of the specific silica particles is within the above range, the content of the nitrogen-containing compound is high, excessive charging is unlikely to occur, and narrowing of the charge distribution is easily realized. As a result, image unevenness and toner scattering are easily suppressed by narrowing the charge distribution of the silica particles under specific conditions.

In the specific silica particles, when Ra and Rb are the volume resistivities of the silica particles before and after firing at 350°C, respectively, Ra/Rb is preferably 0.01 or more and 0.8 or less, and 0.015 or more and 0.01 or more. More preferably 6 or less.
When Ra/Rb is within the above range, the content of the nitrogen element-containing compound is high, excessive charging is less likely to occur, and the charging distribution is more likely to be narrowed. As a result, it becomes easier to suppress image unevenness and toner scattering by narrowing the charge distribution of the silica particles.

Firing at 350°C is carried out as described above.
On the other hand, volume resistivity is measured as follows. Note that the measurement environment is a temperature of 20° C. and a humidity of 50% RH.
Silica particles to be measured are placed on the surface of a circular jig equipped with a 20 cm ² electrode plate to a thickness of approximately 1 mm or more and 3 mm or less to form a silica particle layer. A 20 cm ² electrode plate similar to the above was placed on top of this and the silica particle layer was sandwiched therebetween. In order to eliminate voids between silica particles, a pressure of 0.4 MPa is applied to the electrode plate placed on the silica particle layer, and then the thickness (cm) of the silica particle layer is measured. Both electrodes above and below the silica particle layer are connected to an impedance analyzer (manufactured by Solartron Analytical I), which measures frequencies from 10 ⁻³ Hz to 10 ⁶ Hz to obtain a Nyquist plot. Assuming that there are three types of resistance components: and electrode contact resistance, the bulk resistance R is determined by fitting to an equivalent circuit.
The formula for calculating the volume resistivity (Ω·cm) of silica particles is as shown in the formula below.
・Formula: ρ=R/L
In the formula, ρ represents the volume resistivity (Ω·cm) of the silica particles, R represents the bulk resistance (Ω), and L represents the thickness (cm) of the silica particle layer.

(OH group amount)
In the specific silica particles, the amount of OH groups measured by the Sears method is preferably 0.2 to ^5.5 groups/nm ² and suppresses fogging, clouding, and the like by narrowing the charge distribution of the silica particles. From the viewpoint of suppressing a decrease in fine line reproducibility, 0.2 pieces/nm ² or more and 4 pieces/nm ² or less are more preferable, and 0.2 pieces/nm ² or more and 3 pieces/nm ² or less are even more preferable.
The amount of OH groups measured by the Sears method can be adjusted within the above range by forming a structure composed of a reaction product of a trifunctional silane coupling agent in the silica mother particles.

By reducing the amount of OH groups that inhibit the adsorption of nitrogen element-containing compounds to the above range, the nitrogen element-containing compounds can easily enter deep into the pores of the silica particles (for example, the pores of the adsorption layer described later). Then, the hydrophobic interaction with the nitrogen element-containing compound acts to strengthen the adhesion to the silica particles. Therefore, the amount of nitrogen element-containing compounds adsorbed increases. In addition, it becomes difficult for the nitrogen element-containing compound to be removed. Therefore, the narrowing of the charge distribution by the nitrogen element-containing compound is improved, and the ability to maintain the narrow charge distribution is also improved. As a result, it becomes easier to suppress image unevenness and toner scattering by narrowing the charge distribution of the silica particles.

In addition, by reducing the amount of OH groups to the above range, the environmental dependence of charging characteristics is reduced, so that nitrogen element-containing compounds can be This makes it easier to narrow the charge distribution. As a result, it becomes easier to suppress image unevenness and toner scattering by narrowing the charge distribution of silica particles under specific conditions.

The amount of OH groups is measured by the Sears method, specifically as follows.
1.5 g of silica particles is added to a mixture of 50 g of pure water and 50 g of ethanol, and stirred for 2 minutes with an ultrasonic homogenizer to prepare a dispersion. While stirring in an environment of 25°C, 1.0 g of 0.1 mol/L hydrochloric acid aqueous solution is dropped to obtain a test solution. The obtained test solution is placed in an automatic titration device, and potentiometric titration is performed with 0.01 mol/L sodium hydroxide aqueous solution to prepare a differential curve of the titration curve. Among the inflection points where the differential value of the titration curve is 1.8 or more, the titration amount where the titration amount of the 0.01 mol/L sodium hydroxide aqueous solution is the largest is designated as H.
The surface silanol group density ρ (number/nm ² ) of the silica particles is calculated using the following formula: ρ=((0.01×H−0.1)×NA/1000)/(U×S _BET ×10 ¹⁸ ).
In the formula, the details of the symbols are as follows:
H: the titration amount at which the titration amount of 0.01 mol/L sodium hydroxide aqueous solution is the largest among the inflection points at which the differential value of the titration curve is 1.8 or more; NA: Avogadro's number; U: amount of silica particles (1.5 g);
S _BET : Specific surface area of silica particles (m ² /g) The specific surface area of silica particles is measured by a BET nitrogen adsorption three-point method, with the equilibrium relative pressure being 0.3.

-Production method of specific silica particles-
An example of a method for producing specific silica particles is
A first step of forming a structure composed of a reaction product of a trifunctional silane coupling agent on the surface of at least a portion of the silica mother particles;
a second step of adsorbing a nitrogen element-containing compound containing molybdenum element into at least a portion of the pores of the reaction product of the trifunctional silane coupling agent;
has.
The method for producing specific silica particles includes coating at least a portion of the surface of the silica mother particles after or during the second step, and comprising a reaction product of a trifunctional silane coupling agent, and The silica mother particles having a structure in which a nitrogen element-containing compound containing a molybdenum element is adsorbed to at least a part of the pores of the reaction product of the silane coupling agent may further include a third step of performing a hydrophobization treatment. good.

Hereinafter, the steps of the method for producing specific silica particles will be explained in detail.
[Preparation process]
First, the process of preparing silica mother particles will be explained.
As a preparation process, for example,
(i) A step of preparing a silica mother particle suspension by mixing a solvent containing alcohol and silica mother particles; (ii) A step of granulating the silica mother particles by a sol-gel method to obtain a silica mother particle suspension, etc. can be mentioned.
The silica base particles used in the above (i) include sol-gel silica particles (silica particles obtained by a sol-gel method), aqueous colloidal silica particles, alcoholic silica particles, faded silica particles obtained by a gas phase method, and fused silica particles. etc.
The alcohol-containing solvent used in (i) above may be a solvent containing only alcohol, or may be a mixed solvent of alcohol and other solvents. Examples of the alcohol include lower alcohols such as methanol, ethanol, n-propanol, isopropanol, and butanol. Examples of other solvents include water; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, and acetic acid cellosolve; ethers such as dioxane and tetrahydrofuran; and the like. In the case of a mixed solvent, the proportion of alcohol is preferably 80% by mass or more, more preferably 85% by mass or more.

Step (1-a) is preferably a step of granulating silica mother particles by a sol-gel method to obtain a silica mother particle suspension.
More specifically, step (1-a) includes, for example,
an alkaline catalyst solution preparation step of preparing an alkaline catalyst solution containing an alkaline catalyst in a solvent containing alcohol;
A silica mother particle generation step of supplying tetraalkoxysilane and an alkali catalyst into an alkaline catalyst solution to generate silica mother particles;
A sol-gel method including the following is preferable.

The alkaline catalyst solution preparation step is preferably a step of preparing an alcohol-containing solvent and mixing this solvent with an alkali catalyst to obtain an alkaline catalyst solution.

The alcohol-containing solvent may be a solvent containing alcohol alone, or may be a mixed solvent of alcohol and other solvents. Examples of the alcohol include lower alcohols such as methanol, ethanol, n-propanol, isopropanol, and butanol. Examples of other solvents include water; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, and acetic acid cellosolve; ethers such as dioxane and tetrahydrofuran; and the like. In the case of a mixed solvent, the proportion of alcohol is preferably 80% by mass or more, more preferably 85% by mass or more.

The alkaline catalyst is a catalyst for promoting the reaction (hydrolysis reaction and condensation reaction) of tetraalkoxysilane. Examples of the alkaline catalyst include basic catalysts such as ammonia, urea, and monoamines, with ammonia being particularly preferred.
The concentration of the alkali catalyst in the alkali catalyst solution is preferably 0.5 mol/L or more and 1.5 mol/L or less, more preferably 0.6 mol/L or more and 1.2 mol/L or less, and even more preferably 0.65 mol/L or more and 1.1 mol/L or less.

In the silica base particle generation process, a tetraalkoxysilane and an alkali catalyst are respectively supplied into an alkaline catalyst solution, and the tetraalkoxysilane is reacted (hydrolysis reaction and condensation reaction) in the alkaline catalyst solution to generate silica base particles. This is the process of
In the silica base particle generation process, after core particles are generated by the reaction of tetraalkoxysilane at the initial stage of supply of tetraalkoxysilane (nucleus particle generation stage), this core particle grows (nucleus particle growth stage), and then silica base particles is generated.

Examples of tetraalkoxysilanes include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane. From the viewpoint of controllability of the reaction rate or uniformity of the shape of the resulting silica base particles, tetramethoxysilane or tetraethoxysilane is preferred.

Examples of the alkali catalyst supplied to the alkali catalyst solution include basic catalysts such as ammonia, urea, monoamines, and quaternary ammonium salts, with ammonia being particularly preferred. The alkali catalyst supplied together with the tetraalkoxysilane may be of the same type as the alkali catalyst already contained in the alkali catalyst solution, or may be of a different type, but is preferably of the same type.
The method for supplying the tetraalkoxysilane and the alkali catalyst into the alkali catalyst solution may be a method for supplying them continuously or intermittently.

In the silica base particle production process, the temperature of the alkaline catalyst solution (temperature at the time of supply) is preferably 5°C or higher and 50°C or lower, and more preferably 15°C or higher and 45°C or lower.

[First step]
In the first step, a structure composed of a reaction product of a trifunctional silane coupling agent is formed.
Specifically, in the first step, for example, a trifunctional silane coupling agent is added to a silica base particle suspension, and the trifunctional silane coupling agent is reacted with the surfaces of the silica base particles to form a structure composed of a reaction product of the trifunctional silane coupling agent. The trifunctional silane coupling agent reacts with its functional groups and with OH groups on the surfaces of the silica particles to form a structure composed of the reaction product of the trifunctional silane coupling agent.

The reaction of the trifunctional silane coupling agent is carried out by adding the trifunctional silane coupling agent to the silica mother particle suspension and then heating the suspension while stirring.
Specifically, for example, the suspension is heated to 40° C. or higher and 70° C., and the trifunctional silane coupling agent is added, followed by stirring. The duration of stirring is preferably 10 minutes or more and 24 hours or less, more preferably 60 minutes or more and 420 minutes or less, and even more preferably 80 minutes or more and 300 minutes or less.

[Second process]
In the second step, a nitrogen element-containing compound is adsorbed into at least a portion of the pores of the reaction product of the trifunctional silane coupling agent.
Specifically, in the second step, first, for example, a nitrogen element-containing compound is added to the silica mother particle suspension, and the mixture is stirred at a temperature range of, for example, 20° C. or higher and 50° C. or lower. Thereby, the nitrogen element-containing compound is adsorbed to at least a portion of the pores of the reaction product of the trifunctional silane coupling agent.

In the second step, for example, an alcohol liquid containing a nitrogen element-containing compound may be added to the silica particle suspension.
The alcohol may be the same type as the alcohol contained in the silica base particle suspension or may be a different type, but it is more preferable that the alcohol be the same type.
In the alcohol liquid containing the nitrogen-containing compound, the concentration of the nitrogen-containing compound is preferably 0.05% by mass or more and 10% by mass or less, and more preferably 0.1% by mass or more and 6% by mass or less.

[Third step]
In the third step, after or during the second step, silica mother particles having a structure in which a nitrogen element-containing compound is adsorbed in at least a part of the pores of the reaction product of the trifunctional silane coupling agent are used. , perform hydrophobic treatment.
Specifically, in the third step, for example, a nitrogen element-containing compound is added to the silica mother particle suspension in which the structure is formed, and then a hydrophobizing agent is added.
In the hydrophobizing agent, the functional groups of the hydrophobizing agent react with each other, and the functional groups of the hydrophobizing agent and the OH groups of the silica mother particles react to form a hydrophobizing layer.

The reaction of the hydrophobizing agent is carried out by adding a trifunctional silane coupling agent to a suspension of silica base particles, and then heating the suspension while stirring it.
Specifically, for example, the suspension is heated to 40° C. to 70° C., the hydrophobizing agent is added, and then the suspension is stirred. The stirring is continued for preferably 10 minutes to 24 hours, more preferably 20 minutes to 120 minutes, and even more preferably 20 minutes to 90 minutes.

[Drying process]
In the method for producing the specific silica particles, it is preferable to carry out a drying step of removing the solvent from the suspension after carrying out the second step or the third step. The drying step may be carried out during the second step or the third step.

The drying method includes, for example, heat drying, spray drying, and supercritical drying.
Spray drying can be performed by a conventional method using a commercially available spray dryer (disk rotation type, nozzle type, etc.). For example, spraying is performed by spraying the spray liquid into a hot air stream at a rate of 0.2 liters/hour to 1 liter/hour. In this case, the temperature of the hot air is preferably in the range of 70°C to 400°C at the inlet temperature and 40°C to 120°C at the outlet temperature. Here, if the inlet temperature is less than 70°C, the solids contained in the dispersion are not sufficiently dried. If it exceeds 400°C, the shape of the particles is distorted during spray drying. If the outlet temperature is less than 40°C, the solids are not dried sufficiently and adhere to the inside of the device. A more preferable inlet temperature is in the range of 100°C to 300°C.
The silica particle concentration in the silica particle suspension during spray drying is preferably in the range of 10% by mass or more and 30% by mass or less in terms of solid content.

In supercritical drying, the solvent is removed by a supercritical fluid, so that the surface tension between particles is less likely to act, and the primary particles contained in the suspension are dried in a state in which aggregation is suppressed, making it easier to obtain silica particles with a high particle size uniformity.
Examples of substances used as supercritical fluids include carbon dioxide, water, methanol, ethanol, acetone, etc. From the viewpoints of processing efficiency and suppressing the generation of coarse particles, the solvent removal step is preferably a step using supercritical carbon dioxide.

Specifically, supercritical drying is performed, for example, by the following operation.
After storing the suspension in a closed reactor and then introducing liquefied carbon dioxide, the closed reactor is heated and the pressure inside the closed reactor is increased using a high-pressure pump to bring the carbon dioxide in the closed reactor to a supercritical state. do. Then, by flowing liquefied carbon dioxide into the closed reactor and letting supercritical carbon dioxide flow out from the closed reactor, supercritical carbon dioxide is made to flow through the suspension in the closed reactor. While the supercritical carbon dioxide is flowing through the suspension, the solvent is dissolved in the supercritical carbon dioxide, and the solvent is removed along with the supercritical carbon dioxide flowing out of the closed reactor.
The temperature and pressure in the closed reactor described above are such that carbon dioxide becomes supercritical. Where the critical point of carbon dioxide is 31.1° C./7.38 MPa, the temperature and pressure are, for example, 40° C. or higher and 200° C. or higher/pressure 10 MPa or higher and 30 MPa or lower.
The flow rate of the supercritical fluid in supercritical drying is preferably 80 mL/sec or more and 240 mL/sec or less.

The obtained specific silica particles are preferably crushed or sieved as necessary to remove coarse particles and aggregates. Crushing is performed, for example, by a dry grinding device such as a jet mill, a vibration mill, a ball mill, or a pin mill. Sieving is performed, for example, by a vibration sieve or a wind sieving machine.
The amount (content) of the specific silica particles added externally is, for example, preferably from 0.25% by mass to 2.0% by mass, and more preferably from 0.5% by mass to 1.5% by mass, based on the toner particles.

-Other external additives-
As the external additive, other external additives other than the specific silica particles may be used in combination.
Other external additives include inorganic particles and organic particles other than the specific silica particles.
Examples of other inorganic particles include silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, chromium oxide, cerium oxide, magnesium oxide, zirconium oxide, silicon carbide, and nitride. Examples include particles such as silicon.

The surface of the other inorganic particles may be subjected to hydrophobic treatment. The hydrophobic treatment may be performed, for example, by immersing the inorganic particles in a hydrophobic treatment agent. The hydrophobic treatment agent is not particularly limited, and examples thereof include silane coupling agents, silicone oils, titanate coupling agents, and aluminum coupling agents. These may be used alone or in combination of two or more.
The amount of the hydrophobizing agent is usually, for example, 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the other inorganic particles.

Examples of the organic particles include resin particles (resin particles such as polystyrene, polymethyl methacrylate (PMMA), and melamine resin).
The amount (content) of other external additives to be added to the toner particles is preferably 0.05% by mass or more and 5.0% by mass or less, and 0.5% by mass or more and 3.0% by mass. The following are more preferred.

(Toner manufacturing method)
Next, a method for manufacturing toner according to this embodiment will be described.
The toner according to the present embodiment is obtained by externally adding an external additive to the toner particles, if necessary, after producing the toner particles.

The toner particles may be produced by any of a dry production method (e.g., a kneading and pulverizing method, etc.) and a wet production method (e.g., an aggregation-coalescence method, a suspension polymerization method, a dissolution-suspension method, etc.) The method for producing the toner particles is not particularly limited, and a well-known production method is adopted.
Among these, it is preferable to obtain toner particles by the aggregation and coalescence method.

Specifically, for example, when toner particles are manufactured by an aggregation coalescence method, there is a step of preparing a resin particle dispersion in which resin particles serving as a binder resin are dispersed (resin particle dispersion preparation step); A process of agglomerating resin particles (and other particles as necessary) in a dispersion liquid (in a dispersion liquid after mixing other particle dispersions as necessary) to form aggregated particles (agglomerated particle formation). The toner particles Manufacture.

Each step will be described in detail below.
In the following description, a method for obtaining toner particles containing a colorant and a release agent will be described, but the colorant and the release agent are used as necessary. Of course, additives other than the colorant and the release agent may be used.

-Resin particle dispersion preparation process-
First, together with a resin particle dispersion in which resin particles serving as a binder resin are dispersed, for example, a colorant particle dispersion in which colorant particles are dispersed and a release agent particle dispersion in which release agent particles are dispersed are prepared. do.
Here, the resin particle dispersion liquid is prepared, for example, by dispersing resin particles in a dispersion medium using a surfactant.
Examples of the dispersion medium used in the resin particle dispersion include an aqueous medium.
Examples of the aqueous medium include water such as distilled water and ion-exchanged water, alcohols, and the like. These may be used alone or in combination of two or more.

Examples of the surfactant include anionic surfactants such as sulfate salts, sulfonates, phosphates, and soaps; cationic surfactants such as amine salts and quaternary ammonium salts; and nonionic surfactants such as polyethylene glycols, alkylphenol ethylene oxide adducts, and polyhydric alcohols. Among these, anionic surfactants and cationic surfactants are particularly preferred. The nonionic surfactants may be used in combination with anionic surfactants or cationic surfactants.
The surfactant may be used alone or in combination of two or more kinds.

In the resin particle dispersion, examples of the method for dispersing the resin particles in the dispersion medium include general dispersion methods using, for example, a rotary shear type homogenizer, a ball mill having a media, a sand mill, a dyno mill, etc. Depending on the type of resin particles, the resin particles may be dispersed in the resin particle dispersion using, for example, a phase inversion emulsification method.
The phase inversion emulsification method is a method in which the resin to be dispersed is dissolved in a hydrophobic organic solvent in which the resin is soluble, a base is added to the organic continuous phase (O phase) to neutralize it, and then an aqueous medium (W phase) is added to effect conversion of the resin from W/O to O/W (so-called phase inversion) to form a discontinuous phase, and the resin is dispersed in the aqueous medium in the form of particles.

The volume average particle size of the resin particles dispersed in the resin particle dispersion is, for example, preferably from 0.01 μm to 1 μm, more preferably from 0.08 μm to 0.8 μm, and even more preferably from 0.1 μm to 0.6 μm.
The volume average particle size of the resin particles is measured by using a particle size distribution obtained by measurement using a laser diffraction particle size distribution measuring device (for example, LA-700 manufactured by Horiba, Ltd.), subtracting a cumulative distribution from the small particle size side for the volume of a divided particle size range (channel), and measuring the particle size at which the cumulative distribution is 50% of all particles as the volume average particle size D50v. The volume average particle sizes of particles in other dispersions are also measured in the same manner.

The content of the resin particles contained in the resin particle dispersion is, for example, preferably 5% by mass or more and 50% by mass or less, and more preferably 10% by mass or more and 40% by mass or less.
Note that, in the same manner as the resin particle dispersion, for example, a colorant particle dispersion and a release agent particle dispersion are also prepared. In other words, regarding the volume average particle size, dispersion medium, dispersion method, and content of particles in the resin particle dispersion, the colorant particles dispersed in the colorant particle dispersion and the release agent particle dispersion The same applies to the releasing agent particles to be dispersed.

-Agglomerated particle formation process-
Next, the colorant particle dispersion and the release agent particle dispersion are mixed together with the resin particle dispersion.
Then, in the mixed dispersion, the resin particles, the colorant particles, and the release agent particles are hetero-aggregated to form aggregated particles containing the resin particles, the colorant particles, and the release agent particles and having a diameter close to that of the target toner particles.
Specifically, for example, an aggregating agent is added to the mixed dispersion, the pH of the mixed dispersion is adjusted to be acidic (e.g., pH 2 or more and 5 or less), a dispersion stabilizer is added as necessary, and then the mixed dispersion is heated to a temperature of the glass transition temperature of the resin particles (specifically, for example, a temperature of the glass transition temperature of the resin particles -30°C or more and the glass transition temperature -10°C or less), and the particles dispersed in the mixed dispersion are aggregated to form aggregated particles.
In the aggregated particle formation step, for example, the above-mentioned aggregating agent may be added to the mixed dispersion at room temperature (e.g., 25° C.) while stirring the mixed dispersion with a rotary shear homogenizer, the pH of the mixed dispersion may be adjusted to an acidic state (e.g., a pH of 2 or more and 5 or less), and a dispersion stabilizer may be added as necessary, followed by the above-mentioned heating.

Examples of the flocculant include a surfactant having a polarity opposite to that of the surfactant used as the dispersant added to the mixed dispersion, an inorganic metal salt, and a divalent or higher metal complex. In particular, when a metal complex is used as the flocculant, the amount of the surfactant used is reduced, and the charging characteristics are improved.
If necessary, an additive that forms a complex or a similar bond with the metal ions of the flocculant may be used, and a chelating agent is preferably used as this additive.

Examples of inorganic metal salts include metal salts such as calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, aluminum chloride, and aluminum sulfate, as well as inorganic metal salt polymers such as polyaluminum chloride, polyaluminum hydroxide, and calcium polysulfide.
The chelating agent may be a water-soluble chelating agent, such as oxycarboxylic acid (e.g., tartaric acid, citric acid, gluconic acid, etc.), iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA), etc.
The amount of the chelating agent added is, for example, preferably 0.01 parts by mass or more and 5.0 parts by mass or less, and more preferably 0.1 parts by mass or more and less than 3.0 parts by mass, per 100 parts by mass of the resin particles.

-Fusion/unification process-
Next, the agglomerated particle dispersion liquid in which the agglomerated particles are dispersed is heated, for example, to a temperature higher than the glass transition temperature of the resin particles (for example, a temperature higher than the glass transition temperature of the resin particles by 10 to 30 degrees Celsius), and the agglomerated particles are heated to a temperature higher than the glass transition temperature of the resin particles. fuse and coalesce to form toner particles.

Through the above steps, toner particles are obtained.
Note that after obtaining the aggregated particle dispersion liquid in which the aggregated particles are dispersed, the aggregated particle dispersion liquid and the resin particle dispersion liquid in which the resin particles are dispersed are further mixed to further coat the surface of the aggregated particles with resin particles. a step of agglomerating so as to adhere to form a second agglomerated particle; heating a second agglomerated particle dispersion liquid in which the second agglomerated particles are dispersed to fuse and coalesce the second agglomerated particles; The toner particles may be manufactured through a step of forming toner particles having a core/shell structure.

After the fusion and coalescence process, the toner particles formed in the solution are subjected to a known washing process, a solid-liquid separation process, and a drying process to obtain toner particles in a dried state.
In the washing step, it is preferable to carry out sufficient replacement washing with ion-exchanged water from the viewpoint of electrostatic charge. In addition, the solid-liquid separation step is not particularly limited, but it is preferable to carry out suction filtration, pressure filtration, etc. from the viewpoint of productivity. In addition, in the drying step, there is no particular limit to the method, but it is preferable to carry out freeze drying, air flow drying, fluidized drying, vibration type fluidized drying, etc. from the viewpoint of productivity.

The toner according to the present embodiment is manufactured, for example, by adding and mixing external additives to the obtained dry toner particles. Mixing may be carried out using, for example, a V-blender, Henschel mixer, Roedige mixer, or the like. Furthermore, if necessary, coarse toner particles may be removed using a vibrating sieve, a wind sieve, or the like.

(Career)
The carrier according to this embodiment will be described in detail below.
The carrier according to the present embodiment has a dielectric loss factor of 0.5 or more and 2.0 or less. As long as the dielectric loss factor is within the above range, the carrier is not particularly limited, and may be any known carrier. Examples of the carrier include a coated carrier in which the surface of a core material made of magnetic powder is coated with a coating resin; a magnetic powder dispersion type carrier in which magnetic powder is dispersed and mixed in a matrix resin; and a resin impregnated type carrier in which porous magnetic powder is impregnated with resin.
The magnetic powder dispersion type carrier and the resin impregnated type carrier may be a carrier in which the constituent particles of the carrier are used as a core material and are coated with a coating resin.

The core material is preferably a particulate magnetic powder, that is, magnetic particles, because this makes it easier to adjust the dielectric loss factor of the carrier.
The volume average particle size of the magnetic particles is preferably, for example, 20 μm or more and 50 μm or less.
Examples of magnetic particles include magnetic metals such as iron, nickel, and cobalt, and magnetic oxides such as ferrite and magnetite.
In this embodiment, it is preferable that the magnetic particles of the core material contain ferrite having the following formula (1). By containing the ferrite represented by formula (1) in the magnetic particles, it is easy to adjust the dielectric loss factor of the carrier of this embodiment to a desired range.

(MO) _j (Fe ₂ O ₃ ) _k Formula (1)
In formula (1), k represents a numerical value of 1.20 or more and 1.45 or less, and j represents a numerical value of 3-2k. M represents a metal element, and the metal element includes at least Mg.
With respect to the ferrite composition ratio Fe:M=2:1, dielectricity is increased by increasing Fe. Therefore, in formula (1), k is preferably a numerical value of 1.20 or more and 1.45 or less, and more preferably a numerical value of 1.25 or more and 1.30 or less.
M in formula (1) is mainly Mg, but is also a combination of at least one selected from the group consisting of Ti, Zr, Mn, Sr, Si, Li, Ca, Sn, Cu, Zn, and Ba. Good too. From the viewpoint of increasing the dielectricity of the carrier and reducing charge leakage in the developer, the content of Mg per mol of Fe is preferably 0.04 mol or more and 0.20 mol or less, and more preferably 0.07 mol or more and 0.15 mol or less. is preferred. For the same purpose, Mn may be contained in addition to Mg, and when used together with Mg, the content of Mn per mol of Fe is preferably 0.002 mol or more and 0.05 mol or less, and more preferably 0.003 mol or more and 0.05 mol or less. 0.004 mol or less is preferable.

It is also preferable to contain Ti and Zr. As the Fe content increases, the iron oxide becomes ferrite and the crystals grow, increasing the dielectric properties, but since ferrite is conductive, the dielectric properties increase and at the same time the electrical resistance decreases, making it more likely for charge leakage to occur. The presence of Ti and Zr suppresses charge leakage and has little adverse effect on the dielectric properties.
The content of Ti relative to 1 mole of Fe is preferably 0.02 moles or more and 0.05 moles or less, more preferably 0.03 moles or more and 0.04 moles or less. The content of Zr relative to 1 mole of Fe is preferably 0.014 moles or more and 0.018 moles or less, more preferably 0.0153 moles or more and 0.016 moles or less. Either Ti or Zr may be contained, but they can also be used in combination.
It is also possible to contain other metal elements such as Sr, Si, etc. The content per mole of Fe is preferably 0.001 mole or more and 0.03 mole or less, and more preferably 0.003 mole or more and 0.02 mole or less.
As described above, the dielectric loss factor of the carrier can be adjusted by selecting each metal.

In this embodiment, the composition of the ferrite contained in the magnetic particles and the content of metals such as Mg, Mn, Ti, and Zr relative to 1 mol of Fe contained in the magnetic particles are determined by the following method.
The constituent elements can be identified by fluorescent X-rays. The content can also be measured using a calibration curve from quantitative analysis. The mole number can be obtained by dividing the content by the atomic weight, and the molar ratio of each element to Fe can be obtained from the ratio.

In this embodiment, examples of the coating resin and matrix resin used for the carrier include polyethylene, polypropylene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl ether, polyvinyl ketone, and vinyl chloride-vinyl acetate. Copolymers, styrene-acrylic acid ester copolymers, straight silicone resins containing organosiloxane bonds or modified products thereof, fluororesins, polyesters, polycarbonates, phenolic resins, epoxy resins, and the like can be mentioned.
Note that the coating resin and the matrix resin may contain other additives such as conductive particles.
Examples of the conductive particles include particles of metals such as gold, silver, and copper, carbon black, titanium oxide, zinc oxide, tin oxide, barium sulfate, aluminum borate, and potassium titanate.

Here, the surface of the core material can be coated with the coating resin by a method of coating with a coating layer forming solution in which the coating resin and, if necessary, various additives are dissolved in a suitable solvent. The solvent is not particularly limited and may be selected in consideration of the coating resin used, coating suitability, etc.
Specific resin coating methods include a dipping method in which the core material is immersed in a solution for forming a coating layer, a spray method in which the solution for forming a coating layer is sprayed onto the surface of the core material, and a method in which the core material is suspended in fluidized air. Examples include a fluidized bed method in which a coating layer forming solution is sprayed, and a kneader coater method in which a carrier core material and a coating layer forming solution are mixed in a kneader coater and the solvent is removed.

In addition, the mass ratio of the specific silica particles to the carrier (silica/carrier) is preferably 0.03 or more and 0.15 or less, more preferably 0.05 or more and 0.12 or less, and even more preferably 0.07 or more and 0.10 or less, from the viewpoints of generating appropriate repulsion between the silica particles and the carrier, maintaining stable charging characteristics, and suppressing charge leakage.
The mixing ratio (mass ratio) of the toner and the carrier is preferably in the range of 1:100 to 30:100, and more preferably in the range of 3:100 to 20:100.

<Image forming apparatus, image forming method>
An image forming apparatus/image forming method according to this embodiment will be described.
The image forming apparatus according to the present embodiment includes an image carrier, a charging means for charging the surface of the image carrier, an electrostatic image forming means for forming an electrostatic charge image on the surface of the charged image carrier, and an electrostatic charge image forming means for forming an electrostatic charge image on the surface of the charged image carrier. a developing means that contains an image developer and develops the electrostatic image formed on the surface of the image carrier as a toner image by the electrostatic charge image developer; and a fixing means for fixing the toner image transferred to the surface of the recording medium. The electrostatic image developer according to this embodiment is applied as the electrostatic image developer.

The image forming apparatus according to the present embodiment includes a charging process of charging the surface of the image carrier, an electrostatic image forming process of forming an electrostatic charge image on the surface of the charged image carrier, and an electrostatic charge according to the present embodiment. a developing step of developing an electrostatic charge image formed on the surface of the image carrier as a toner image with an image developer; a transfer step of transferring the toner image formed on the surface of the image carrier onto the surface of a recording medium; An image forming method (image forming method according to this embodiment) including a fixing step of fixing a toner image transferred to the surface of a recording medium is carried out.

The image forming apparatus according to the present embodiment may be any of known image forming apparatuses, such as a direct transfer type apparatus in which a toner image formed on the surface of an image holder is directly transferred to a recording medium; an intermediate transfer type apparatus in which a toner image formed on the surface of an image holder is primarily transferred to the surface of an intermediate transfer body, and the toner image transferred to the surface of the intermediate transfer body is secondarily transferred to the surface of a recording medium; an apparatus equipped with a cleaning means for cleaning the surface of the image holder after the transfer of the toner image and before charging; and an apparatus equipped with a discharging means for irradiating the surface of the image holder with discharging light to discharge it after the transfer of the toner image and before charging it.
When the image forming apparatus according to the present embodiment is an intermediate transfer type apparatus, the transfer means has, for example, an intermediate transfer body onto whose surface a toner image is transferred, a primary transfer means which primarily transfers the toner image formed on the surface of the image carrier onto the surface of the intermediate transfer body, and a secondary transfer means which secondarily transfers the toner image transferred onto the surface of the intermediate transfer body onto the surface of a recording medium.

In the image forming apparatus according to the present embodiment, for example, the portion including the developing means may be a cartridge structure (process cartridge) that is detachable from the image forming apparatus. As the process cartridge, for example, a process cartridge including a developing means containing the electrostatic image developer according to the present embodiment is suitably used.

An example of an image forming apparatus according to the present embodiment will be described below, but the present invention is not limited thereto. In the following explanation, the main parts shown in the figures will be explained, and the explanation of the others will be omitted.

FIG. 1 is a schematic diagram showing the configuration of an image forming apparatus according to the present embodiment.
The image forming apparatus shown in Fig. 1 includes first to fourth image forming units 10Y, 10M, 10C, and 10K (image forming means) of an electrophotographic type that output images of each color of yellow (Y), magenta (M), cyan (C), and black (K) based on color-separated image data. These image forming units (hereinafter, sometimes simply referred to as "units") 10Y, 10M, 10C, and 10K are arranged in parallel at predetermined distances from each other in the horizontal direction. These units 10Y, 10M, 10C, and 10K may be process cartridges that are detachably attached to the image forming apparatus.

Above each of the units 10Y, 10M, 10C, and 10K, an intermediate transfer belt (an example of an intermediate transfer body) 20 is provided, which extends through each unit. The intermediate transfer belt 20 is provided by being wound around a drive roll 22 and a support roll 24, which are in contact with the inner surface of the intermediate transfer belt 20, and is adapted to run in a direction from the first unit 10Y toward the fourth unit 10K. A force is applied to the support roll 24 by a spring or the like (not shown) in a direction away from the drive roll 22, and tension is applied to the intermediate transfer belt 20 wound around them. An intermediate transfer belt cleaning device 30 is provided on the image bearing surface side of the intermediate transfer belt 20, facing the drive roll 22.
The developing devices (examples of developing means) 4Y, 4M, 4C, and 4K of the units 10Y, 10M, 10C, and 10K are supplied with yellow, magenta, cyan, and black toners contained in toner cartridges 8Y, 8M, 8C, and 8K, respectively.

The first to fourth units 10Y, 10M, 10C, and 10K have the same configuration and operation, so here we will explain the first unit 10Y, which forms a yellow image and is arranged upstream in the direction in which the intermediate transfer belt travels, as a representative unit.

The first unit 10Y has a photoreceptor 1Y that acts as an image carrier. Around the photoreceptor 1Y, there is a charging roll (an example of charging means) 2Y that charges the surface of the photoreceptor 1Y to a predetermined potential, and the charged surface is exposed to a laser beam 3Y based on a color-separated image signal. an exposure device (an example of an electrostatic image forming means) 3, a developing device (an example of a developing means) 4Y, which supplies charged toner to an electrostatic image and develops the electrostatic image; A primary transfer roll (an example of primary transfer means) 5Y that transfers the toner image onto the intermediate transfer belt 20, and a photoreceptor cleaning device (an example of image carrier cleaning means) that removes toner remaining on the surface of the photoreceptor 1Y after the primary transfer. Example) 6Y are arranged in order.

The primary transfer roll 5Y is arranged inside the intermediate transfer belt 20, and is provided at a position facing the photoreceptor 1Y. A bias power source (not shown) for applying a primary transfer bias is connected to the primary transfer rolls 5Y, 5M, 5C, and 5K of each unit. Each bias power supply changes the value of the transfer bias applied to each primary transfer roll under the control of a control unit (not shown).

The operation of forming a yellow image in the first unit 10Y will be described below.
First, prior to operation, the surface of the photoreceptor 1Y is charged to a potential of -600V to -800V by the charging roll 2Y.
The photoreceptor 1Y is formed by laminating a photoreceptor layer on a conductive substrate (eg, volume resistivity at 20° C. of 1×10 ⁻⁶ Ωcm or less). This photosensitive layer normally has a high resistance (common resin resistance), but when irradiated with a laser beam, the resistivity of the portion irradiated with the laser beam changes. Therefore, the surface of the charged photoreceptor 1Y is irradiated with a laser beam 3Y from the exposure device 3 according to image data for yellow sent from a control section (not shown). As a result, an electrostatic charge image of a yellow image pattern is formed on the surface of the photoreceptor 1Y.

An electrostatic charge image is an image formed on the surface of the photoconductor 1Y due to electrical charging, and the laser beam 3Y reduces the specific resistance of the irradiated portion of the photoconductor layer, causing the charged charges on the surface of the photoconductor 1Y to flow. , on the other hand, is a so-called negative latent image formed by residual charges in areas not irradiated with the laser beam 3Y.
The electrostatic charge image formed on the photoreceptor 1Y rotates to a predetermined development position as the photoreceptor 1Y travels. At this developing position, the electrostatic charge image on the photoreceptor 1Y is developed and visualized as a toner image by the developing device 4Y.

The developing device 4Y contains, for example, an electrostatic image developer containing at least yellow toner and carrier. The yellow toner is triboelectrically charged by being stirred inside the developing device 4Y, and has an electric charge of the same polarity (negative polarity) as the electric charge charged on the photoreceptor 1Y, and is transferred to the developer roll (developer holder). An example) is held on top. Then, as the surface of the photoreceptor 1Y passes through the developing device 4Y, yellow toner electrostatically adheres to the latent image area on the surface of the photoreceptor 1Y from which the static electricity has been removed, and the latent image is developed with the yellow toner. Ru. The photoconductor 1Y on which the yellow toner image has been formed continues to travel at a predetermined speed, and the toner image developed on the photoconductor 1Y is conveyed to a predetermined primary transfer position.

When the yellow toner image on the photoconductor 1Y is transported to the primary transfer position, a primary transfer bias is applied to the primary transfer roll 5Y, and an electrostatic force from the photoconductor 1Y toward the primary transfer roll 5Y acts on the toner image. The toner image on the photoreceptor 1Y is transferred onto the intermediate transfer belt 20. The transfer bias applied at this time has a (+) polarity opposite to the toner polarity (-), and is controlled to, for example, +10 μA by a control section (not shown) in the first unit 10Y.
On the other hand, the toner remaining on the photoreceptor 1Y is removed and collected by the photoreceptor cleaning device 6Y.

The primary transfer bias applied to the primary transfer rolls 5M, 5C, and 5K of the second unit 10M and subsequent units is also controlled in accordance with the first unit.
In this manner, the intermediate transfer belt 20 onto which the yellow toner image has been transferred by the first unit 10Y is conveyed successively through the second to fourth units 10M, 10C, and 10K, where the toner images of each color are transferred and superimposed.

The intermediate transfer belt 20, to which the four color toner images have been transferred in multiple layers through the first to fourth units, reaches a secondary transfer section consisting of the intermediate transfer belt 20, a support roll 24 in contact with the inner surface of the intermediate transfer belt, and a secondary transfer roll (an example of a secondary transfer means) 26 arranged on the image bearing surface side of the intermediate transfer belt 20. Meanwhile, a recording paper (an example of a recording medium) P is fed at a predetermined timing through a supply mechanism into the gap between the secondary transfer roll 26 and the intermediate transfer belt 20, and a secondary transfer bias is applied to the support roll 24. The transfer bias applied at this time has a (-) polarity that is the same as the (-) polarity of the toner, and an electrostatic force from the intermediate transfer belt 20 toward the recording paper P acts on the toner image, and the toner image on the intermediate transfer belt 20 is transferred onto the recording paper P. The secondary transfer bias at this time is determined according to the resistance detected by a resistance detection means (not shown) that detects the resistance of the secondary transfer section, and is voltage controlled.

The recording paper P with the transferred toner image is fed into the pressure contact portion (nip portion) of a pair of fixing rolls in the fixing device (one example of a fixing means) 28, where the toner image is fixed onto the recording paper P, forming a fixed image. Once the color image has been fixed, the recording paper P is conveyed toward the discharge portion, and the series of color image forming operations is completed.

The recording paper P onto which the toner image is transferred can be, for example, plain paper used in electrophotographic copying machines, printers, etc. In addition to the recording paper P, other examples of the recording medium include overhead projector sheets and the like.
In order to further improve the smoothness of the image surface after fixing, it is preferable that the surface of the recording paper P is also smooth. For example, coated paper in which the surface of ordinary paper is coated with a resin or the like, art paper for printing, etc. are preferably used.

<Process cartridge>
A process cartridge according to this embodiment will be described.
The process cartridge according to the present embodiment contains the electrostatic charge image developer according to the present embodiment, and has a developing means for developing the electrostatic charge image formed on the surface of the image carrier as a toner image using the electrostatic charge image developer. This is a process cartridge that can be attached to and removed from an image forming apparatus.
The process cartridge according to the present embodiment includes a developing means and, if necessary, at least one other means selected from an image carrier, a charging means, an electrostatic image forming means, a transfer means, etc. It may be a configuration.

Below, an example of a process cartridge according to this embodiment is shown, but the invention is not limited to this. In the following explanation, the main parts shown in the figure will be explained, and the explanation of the rest will be omitted.

FIG. 2 is a schematic diagram showing an example of a process cartridge according to the present embodiment.
The process cartridge 200 shown in FIG. 2 is configured by, for example, a housing 117 having mounting rails 116 and an opening 118 for exposure, and integrally holding a photoconductor 107 (an example of an image carrier), a charging roll 108 (an example of a charging means) provided around the photoconductor 107, a developing device 111 (an example of a developing means), and a photoconductor cleaning device 113 (an example of a cleaning means), which are combined and held in a cartridge form.
In FIG. 2, reference numeral 109 denotes an exposure device (an example of an electrostatic image forming means), 112 denotes a transfer device (an example of a transfer means), 115 denotes a fixing device (an example of a fixing means), and 300 denotes a recording paper (an example of a recording medium).

The following provides a detailed explanation of the embodiments of the invention using examples, but the embodiments of the invention are in no way limited to these examples. In the following explanation, "parts" and "%" are by mass unless otherwise specified.

<Preparation of Toner Particles>
(Toner Particles (1))
-Synthesis of amorphous polyester resin-
Bisphenol A ethylene oxide adduct (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.):
150 parts Bisphenol A propylene oxide adduct [manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.]: 250 parts Tetrapropenyl succinic anhydride [manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.]: 130 parts Terephthalic acid [manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.]: 100 parts Trimellitic acid [manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.]: 15 parts The above monomer components were charged into a reaction vessel equipped with a stirrer, a thermometer, a condenser and a nitrogen gas inlet tube, and the reaction vessel was replaced with dry nitrogen gas, and then tin dioctanoate was charged in an amount of 0.3% based on the total amount of the monomer components. The temperature was raised to 235°C over 1 hour under a nitrogen gas stream, and reacted for 3 hours, the pressure in the reaction vessel was reduced to 10.0 mmHg, and the reaction was stirred and terminated when the desired molecular weight was reached.
The resulting amorphous polyester resin had a glass transition temperature of 61° C., a weight average molecular weight of 42,000, and an acid value of 13 mgKOH/g.

-Preparation of amorphous polyester resin dispersion-
- Amorphous polyester resin: 100 parts - Methyl ethyl ketone: 60 parts - Isopropyl alcohol: 10 parts The above components were charged into a reaction vessel equipped with a stirrer and dissolved at 60°C. After confirming dissolution, the reaction vessel was cooled to 35° C., and then 3.5 parts of a 10% ammonia aqueous solution was added.
Next, 300 parts of ion-exchanged water was dropped into the reaction vessel over 3 hours to create a polyester resin dispersion. Next, methyl ethyl ketone and isopropyl alcohol were removed using an evaporator to obtain an amorphous polyester resin dispersion.

-Preparation of colorant particle dispersion-
・Cyan pigment [Pigment Blue 15:3, manufactured by Dainichiseika Industries Co., Ltd.] 10 parts ・Anionic surfactant [Neogen SC, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.] 2 parts ・Ion exchange water 80 parts The above ingredients The mixture was mixed and dispersed for 1 hour using a high-pressure impact dispersion machine Ultimizer [HJP30006, manufactured by Sugino Machine Co., Ltd.] to obtain a colorant particle dispersion having a volume average particle diameter of 180 nm and a solid content of 20%.

-Preparation of release agent particle dispersion-
・Paraffin wax [HNP 9, manufactured by Nippon Seirin Co., Ltd.] 50 parts ・Anionic surfactant [Neogen SC, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.] 2 parts ・Ion exchange water 200 parts The above ingredients were heated to 120°C. After mixing and dispersing using Ultra Turrax T50 manufactured by IKA Corporation, dispersion treatment was performed using a pressure discharge type homogenizer to obtain a release agent particle dispersion having a volume average particle diameter of 200 nm and a solid content of 20%.

-Preparation of toner particles (1)-
・Amorphous polyester resin particle dispersion 210 parts ・Colorant particle aqueous dispersion 25 parts ・Release agent particle dispersion 30 parts ・Polyaluminum chloride 0.4 parts ・Ion exchange water 100 parts The above ingredients were mixed in a stainless steel flask. After mixing and dispersing using an Ultra Turrax manufactured by IKA, the flask was heated to 48° C. while stirring in a heating oil bath. After holding at 48°C for 25 minutes, 70 parts of the same polyester resin dispersion as above was slowly added thereto.

Thereafter, the pH of the system was adjusted to 8.0 using a 0.5 mol/L aqueous sodium hydroxide solution, and the stainless steel flask was sealed, the seal of the stirring shaft was magnetically sealed, and the mixture was heated to 90° C. while continuing stirring, and maintained for 3 hours. After the reaction was completed, the mixture was cooled at a temperature drop rate of 2° C./min, filtered, washed with ion-exchanged water, and then subjected to solid-liquid separation by Nutsche suction filtration. The mixture was further redispersed using 3 L of ion-exchanged water at 30° C., and stirred and washed at 300 rpm for 15 minutes. This washing operation was repeated six more times, and when the pH of the filtrate reached 7.54 and the electrical conductivity reached 6.5 μS/cm, solid-liquid separation was performed using No. 5A filter paper by Nutsche suction filtration. Next, vacuum drying was continued for 12 hours to obtain toner particles (1).
The toner particles (1) had a volume average particle size (D50v) of 6.1 μm and an average circularity of 0.965.

<Preparation of external additives>
[Preparation of Silica Particles]
- Preparation of alkaline catalyst solution -
Into a glass reaction vessel equipped with a metallic stirring rod, a dropping nozzle, and a thermometer, 950 parts of methanol and aqueous ammonia (NH ₄ OH) in the amount and concentration shown in Table 1 were placed, stirred and mixed to obtain an alkaline catalyst solution.
- Granulation of silica base particles by the sol-gel method -
The temperature of the alkaline catalyst solution was adjusted to 40° C., and the alkaline catalyst solution was purged with nitrogen. Next, while stirring the alkaline catalyst solution, tetramethoxysilane (TMOS) in the amount shown in Table 1 and 124 parts of ammonia water (NH ₄ OH) with a catalyst (NH ₃ ) concentration of 7.9% were simultaneously dropped to obtain a silica base particle suspension.

-Addition of trifunctional silane coupling agent-
The silica base particle suspension was heated to 40° C. and stirred, while methyltrimethoxysilane (MTMS) was added as a trifunctional silane coupling agent to the suspension in the amount shown in Table 1. Stirring was then continued for 120 minutes to react the trifunctional silane coupling agent and form an adsorption structure.
- Addition of nitrogen-containing compounds -
The nitrogen-containing compound TP-415, details of which are shown below, or n-hexadecyltrimethylammonium bromide was used in the amounts shown in Table 1, and diluted with butanol to prepare an alcohol solution.
TP-415: [N ⁺ (CH) ₃ (C ₁₄ C ₂₉ ) ₂ ] ₄ Mo ₈ O ₂₈ ^4- (N,N-Dimethyl-N-tetradecyl-1-tetradecaneminium,hexa-μ-oxotetra-μ 3-oxodi-μ 5-oxotetradecaoxooctamolibdate (4-) (4:1) manufactured by Hodogaya Chemical Co., Ltd. Next, an alcoholic solution in which a nitrogen-containing compound was diluted with butanol was added to the suspension. At this time, the alcoholic solution was added so that the number of parts of the nitrogen-containing compound per 100 parts of the solid content of the silica base particle suspension was the amount shown in Table 1. Next, the mixture was stirred at 30° C. for 100 minutes to obtain a suspension containing a nitrogen-containing compound.
- Drying -
Next, 300 parts by mass of the suspension was placed in a reaction vessel, _CO2 was added while stirring, and the temperature and pressure in the reaction vessel were raised to 150°C and 15 MPa. _CO2 was introduced and discharged at a flow rate of 5 L/min while stirring while maintaining the temperature and pressure. Thereafter, the solvent was removed over 120 minutes to obtain silica particles A-1 to A-13.

<Evaluation of Silica Particles>
The following properties of the obtained silica particles were measured according to the methods described above. The measured values for each silica particle are shown in Table 1.
- Number average particle size (referred to as "average particle size" in the table)
- Average circularity - Content of nitrogen element compounds converted into nitrogen element (in the table, this is indicated as "N content (N element conversion)")
The ratio of the net intensity of molybdenum element to the net intensity of silicon element measured by fluorescent X-ray analysis (represented as "Mo/Si" in the table).

<Preparation of carrier core material>
(Preparation of ferrite particles)
The amounts of ferrite materials listed in Table 2 were mixed and mixed and ground using a wet ball mill for 10 hours. Next, it was granulated and dried using a spray dryer, and then pre-calcined 1 at 900° C. for 6 hours using a rotary kiln. The obtained pre-calcined product of pre-calcination 1 was pulverized for 2 hours using a wet ball mill to obtain an average particle size of 2 μm, then further granulated and dried using a spray dryer, and then pre-calcined at 950°C for 6 hours using a rotary kiln. Firing 2 was performed. The obtained pre-calcined product of pre-calcination 2 was pulverized for 5 hours using a wet ball mill to give an average particle size of 5 μm, and then granulated and dried using a spray dryer, followed by an electric furnace at the temperatures listed in Table 2. Baking was performed for 5 hours. After firing, a crushing process and a classification process were performed to obtain ferrite particles 1 to 9 having a particle size of about 35 μm.

<Preparation of carrier 1>
・Toluene 14 parts ・Isopropyl alcohol 4 parts ・Cyclohexyl methacrylate (average molecular weight Mw 50,000) 2 parts ・Carbon black VXC72 (manufactured by Cabot) 0.2 parts The above components were stirred with a stirrer for 10 minutes to prepare a dispersed coating liquid. Next, this coating liquid and 100 parts of ferrite particles 1 are placed in a vacuum degassing type kneader, stirred at 60°C for 30 minutes, and then degassed by reducing the pressure while heating and drying. I got carrier 1.
<Preparation of carriers 2 to 9>
Carriers 2 to 9 were obtained in the same manner as Carrier 1 except that 100 parts of each of ferrite particles 2 to 9 were used instead of ferrite particles 1.

<Evaluation of Carrier Particles>
The toner particles (1) and each carrier were mixed at a toner ratio of 8% to prepare a developer for measurement, which was compression molded to a thickness of 5 mm, and the dielectric loss factor was measured at 6 KHz and 5 V (RSM) using an LCR meter manufactured by Wayne Kerr, Inc. The results are shown in Table 2. The detailed compositions of ferrite particles 1 to 9 are shown in Table 3.

<Preparation of Developer>
To 100 parts of the toner particles (1), silica particles (external additive) of the type shown in Table 4 were added so as to obtain the amount of silica in the toner shown in Table 4, and the mixture was mixed in a Henschel mixer at a stirring peripheral speed of 30 m/sec for 15 minutes to obtain toners of the respective examples and comparative examples.
The obtained toners and carriers 1 to 9 were placed in a V blender in the ratio that corresponds to the "toner ratio in developer" shown in Table 4, and stirred for 20 minutes to obtain the developers of Examples 1 to 21 and Comparative Examples 1 to 4. The weight ratio of silica to carrier (silica/carrier) in each developer is shown in Table 4.

<Evaluation of white spot occurrence>
For each of the developers of Examples 1 to 21 and Comparative Examples 1 to 4, 100 sheets of blank paper were printed using DocuCentreColor 400CP (manufactured by Fujifilm Business Innovation Co., Ltd.) under conditions of 25° C. and 15% RH. Subsequently, 10 sheets of 10 cm square solid printing were performed at half the speed, and the number of white spots (color omissions) in the 10 images was counted.
Table 4 shows the number of white spots in each Example and Comparative Example and the judgment based on the following criteria. Note that ratings A and B are acceptable.
-Evaluation criteria-
A: White point number 0-1
B: Number of white points 2-4
C: Number of white spots: 5 or more As shown in Table 4, it was found that the generation of white spots was suppressed in printing using the developer of the example.

(Additional note)
(((１)))
toner particles;
The silica particles externally added to the toner particles contain a nitrogen element-containing compound containing a molybdenum element, and the net intensity of the molybdenum element and the net intensity of the silicon element in the silica particles are measured by fluorescent X-ray analysis. silica particles whose ratio (Mo/Si) is 0.035 or more and 0.45 or less;
a carrier having a relative dielectric loss factor of 0.5 or more and 2.0 or less;
An electrostatic image developer containing.
(((2)))
The electrostatic image developer according to ((1)), wherein the carrier is made of ferrite, and the ferrite contains at least one of titanium and zirconium.
(((３)))
The electrostatic image developer according to (((1))) or (((2))), wherein the carrier has a relative dielectric loss factor of 0.7 or more and 1.7 or less.
(((４)))
The electrostatic image developer according to (((2))) or (((3))), wherein the ferrite further contains manganese and magnesium.
(((５)))
According to any one of (((1))) to (((4))), the weight ratio of the silica particles and the carrier (silica/carrier) is 0.03 or more and 0.15 or less. electrostatic image developer.
(((６)))
Any of (((1))) to (((5))), wherein the ratio of the net strength of the molybdenum element to the net strength of the silicon element (Mo/Si) is 0.10 or more and 0.30 or less. The electrostatic image developer according to item 1.
(((7)))
The electrostatic image developer according to any one of (((1))) to (((6))), wherein the nitrogen element-containing compound containing a molybdenum element is a quaternary ammonium salt containing a molybdenum element. .
(((８)))
The electrostatic image developer according to any one of (((1))) to ((7)), wherein the silica particles have a number average particle diameter of 10 nm or more and 100 nm or less.
(((9)))
The silica particles are
Silica mother particles,
The surface of at least a portion of the silica mother particles is coated with a reaction product of a trifunctional silane coupling agent, and the molybdenum is contained in at least a portion of the pores of the reaction product of the trifunctional silane coupling agent. A structure in which a nitrogen element-containing compound containing the element is adsorbed,
The electrostatic image developer according to ((8)), having:
(((１０)))
(((1))) to (((9))); comprising a developing means for developing the charge image as a toner image,
A process cartridge that can be attached to and removed from an image forming apparatus.
(((１１)))
an image holder;
Charging means for charging the surface of the image carrier;
an electrostatic charge image forming means for forming an electrostatic charge image on the surface of the charged image carrier;
The electrostatic image developer according to any one of ((1)) to ((9))) is contained, and the electrostatic image developer forms an image on the surface of the image carrier. a developing means for developing the electrostatic charge image as a toner image;
a transfer means for transferring the toner image formed on the surface of the image carrier to the surface of a recording medium;
a fixing means for fixing the toner image transferred to the surface of the recording medium;
An image forming apparatus comprising:
(((１２)))
a charging step of charging the surface of the image carrier;
an electrostatic charge image forming step of forming an electrostatic charge image on the surface of the charged image carrier;
Development in which an electrostatic image formed on the surface of the image carrier is developed as a toner image using the electrostatic image developer according to any one of (((1))) to (((9))). process and
a transfer step of transferring the toner image formed on the surface of the image carrier to the surface of a recording medium;
a fixing step of fixing the toner image transferred to the surface of the recording medium;
An image forming method comprising:

According to the invention of (((1))), it is possible to provide an electrostatic image developer or the like that contains toner particles to which silica particles have been externally added and a carrier, in which charge leakage under high temperature and high humidity conditions is suppressed and the occurrence of white spots is suppressed, even when printing is performed with an extremely high image density.
According to the invention of (((2))), the carrier is made of ferrite, and compared to a case in which the ferrite does not contain titanium or zirconium, the dielectric loss factor of the carrier is adjusted, and an electrostatic image developer having appropriate charging properties can be provided.
According to the invention (((3))), it is possible to provide an electrostatic image developer in which the carrier has favorable charging properties and is capable of suppressing the occurrence of charge leakage, compared with a case in which the dielectric loss factor of the carrier is less than 0.7 or exceeds 1.7.
According to the invention (((4))), the dielectric loss factor of the carrier is adjusted and an electrostatic image developer having appropriate charging properties can be provided, compared to a case in which the ferrite in the carrier contains neither manganese nor magnesium.
According to the invention (((5))), compared with a case where the weight ratio of the silica particles to the carrier (silica/carrier) is less than 0.03 or exceeds 0.15, an electrostatic image developer can be provided in which the silica particles have a preferred charge amount and charge leakage through the carrier is suppressed.
According to the invention (((6))), it is possible to provide an electrostatic image developer in which the charging range in silica particles is narrowed, charge leakage is suppressed, and the occurrence of white spots in images is suppressed, as compared with the case in which the ratio (Mo/Si) of the net strength of the molybdenum element to the net strength of the silicon element is less than 0.10 or exceeds 0.30.
According to the invention (((7))), it is possible to provide an electrostatic image developer in which the charge distribution of silica particles is narrower than when the nitrogen-containing compound containing molybdenum is not a quaternary ammonium salt containing molybdenum.
According to the invention (((8))), a suitable repulsion occurs between the carrier and the silica particles, compared with a case in which the number average particle diameter of the silica particles is less than 10 nm or exceeds 100 nm, and an electrostatic image developer with stable charging can be provided.
According to the invention of (((9))), it is possible to provide an electrostatic image developer that can narrow the charge distribution in the silica particles, compared to a structure in which the silica particles are not a structure in which at least a portion of the surface of the silica base particle is coated, the silica particles are composed of a reaction product of a trifunctional silane coupling agent, and the nitrogen-element-containing compound is adsorbed into at least a portion of the pores of the reaction product of the trifunctional silane coupling agent.
According to the invention of (((10))), (((11))) or (((12))), it is possible to provide a process cartridge, an image forming apparatus or an image forming method capable of applying an electrostatic image developer or the like containing toner particles to which silica particles have been externally added and a carrier, in which charge leakage is suppressed under high temperature and high humidity conditions and the occurrence of white spots is suppressed even in printing that requires an extremely high image density.

1Y, 1M, 1C, 1K: Photoconductor (an example of an image carrier)
2Y, 2M, 2C, 2K Charging rolls (an example of a charging means)
3. Exposure device (an example of an electrostatic image forming means)
3Y, 3M, 3C, 3K Laser beams 4Y, 4M, 4C, 4K Developing device (an example of a developing means)
5Y, 5M, 5C, 5K: Primary transfer roll (an example of a primary transfer means)
6Y, 6M, 6C, 6K: photoconductor cleaning device (an example of an image carrier cleaning means) 8Y, 8M, 8C, 8K: toner cartridge 10Y, 10M, 10C, 10K: image forming unit 20: intermediate transfer belt (an example of an intermediate transfer body)
22 Drive roll 24 Support roll 26 Secondary transfer roll (an example of a secondary transfer means)
28 Fixing device (an example of a fixing means)
30 Intermediate transfer belt cleaning device (an example of an intermediate transfer body cleaning means)
P Recording paper (an example of a recording medium)

107 Photoreceptor (an example of an image carrier)
108 Charging roll (an example of charging means)
109 Exposure device (an example of electrostatic image forming means)
111 Developing device (an example of developing means)
112 Transfer device (an example of transfer means)
113 Photoreceptor cleaning device (an example of image carrier cleaning means)
115 Fixing device (an example of fixing means)
116 Mounting rail 117 Housing 118 Opening for exposure 200 Process cartridge 300 Recording paper (an example of recording medium)

Claims (12)

toner particles;
The silica particles externally added to the toner particles contain a nitrogen element-containing compound containing a molybdenum element, and the net intensity of the molybdenum element and the net intensity of the silicon element in the silica particles are measured by fluorescent X-ray analysis. silica particles whose ratio (Mo/Si) is 0.035 or more and 0.45 or less;
a carrier having a relative dielectric loss factor of 0.5 or more and 2.0 or less;
An electrostatic image developer containing. The electrostatic image developer according to claim 1, wherein the carrier is made of ferrite, and the ferrite contains at least one of titanium and zirconium. The electrostatic image developer according to claim 2, wherein the carrier has a relative dielectric loss factor of 0.7 or more and 1.7 or less. The electrostatic image developer according to claim 2, wherein the ferrite further contains manganese and magnesium. The electrostatic image developer according to claim 1, wherein the weight ratio of the silica particles to the carrier (silica/carrier) is 0.03 or more and 0.15 or less. 6. The electrostatic image developer according to claim 5, wherein a ratio (Mo/Si) between the net strength of the molybdenum element and the net strength of the silicon element is 0.10 or more and 0.30 or less. The electrostatic image developer according to claim 6, wherein the nitrogen-containing compound containing molybdenum is a quaternary ammonium salt containing molybdenum. The electrostatic image developer according to claim 1, wherein the number-average particle size of the silica particles is 10 nm or more and 100 nm or less. The silica particles are
Silica base particles;
a structure that covers at least a portion of the surface of the silica base particle, is composed of a reaction product of a trifunctional silane coupling agent, and has the nitrogen-containing compound including molybdenum adsorbed in at least a portion of the pores of the reaction product of the trifunctional silane coupling agent;
9. The electrostatic image developer of claim 8, having the formula: Developing means containing the electrostatic image developer according to any one of claims 1 to 9, and developing an electrostatic image formed on the surface of an image carrier as a toner image using the electrostatic image developer. Equipped with
A process cartridge that can be attached to and removed from an image forming apparatus. An image carrier;
a charging means for charging the surface of the image carrier;
an electrostatic image forming means for forming an electrostatic image on the charged surface of the image carrier;
a developing unit that contains the electrostatic image developer according to any one of claims 1 to 9 and develops the electrostatic image formed on the surface of the image carrier into a toner image by the electrostatic image developer;
a transfer means for transferring the toner image formed on the surface of the image carrier to a surface of a recording medium;
a fixing means for fixing the toner image transferred onto the surface of the recording medium;
An image forming apparatus comprising: a charging step of charging the surface of the image carrier;
an electrostatic charge image forming step of forming an electrostatic charge image on the surface of the charged image carrier;
A developing step of developing the electrostatic image formed on the surface of the image carrier as a toner image using the electrostatic image developer according to any one of claims 1 to 9;
a transfer step of transferring the toner image formed on the surface of the image carrier to the surface of a recording medium;
a fixing step of fixing the toner image transferred to the surface of the recording medium;
An image forming method comprising:

Images